Dynamic light scattering (DLS) and small-angle neutron scattering (SANS) are used to characterize the structure and dynamics of ternary solutions consisting either of rods or "hairy rod" polymers and polystyrene (PS) coils in a solvent composed of chloroform saturated with (<0.5%) formamide (CF). The rods are poly(γ-benzyl-R-L-glutamate) (PBLG), and the hairy rods are two forms of poly(γ-octadecyl-R-L-glutamate)-co-(γ-methyl-R-L-glutamate) with varying amounts of octadecyl substitution. The DLS autocorrelation functions reveal the existence of two relaxation modes that are interpreted in terms of the random phase approximation theory (RPA) as the cooperative and interdiffusive modes. The two relaxation modes are investigated as a function of the total polymer concentration CP and the relative composition x ) Crod/CP as well as the percentage of octadecyl groups along the polyglutamate chain. The different diffusion coefficients that characterize the dynamics in these systems are well described by the RPA theory of polymer mixtures. In addition, the interaction parameter extracted from both the DLS and SANS experiments is found to be negative. These results suggest an attraction between PS and PBLG molecules and that these polymers are therefore compatible. The hairy rod ternary solution diffusion coefficients indicate that as the percentage of hairs on the rod increases, the polymers become more compatible.

The measurement science in realizing and disseminating the unit for pressure in the International System of Units, the pascal (Pa), has been the subject of much interest at the National Institute of Standards and Technology (NIST). Modern optical-based techniques for pascal metrology have been investigated, including multiphoton ionization and cavity ringdown spectroscopy. Work is ongoing to recast the pascal in terms of quantum properties and fundamental constants and in doing so make vacuum metrology consistent with the global trend toward quantum-based metrology. NIST has ongoing projects that interrogate the index of refraction of a gas using an optical cavity for low vacuum, and count background particles in high vacuum to extreme high vacuum using trapped laser-cooled atoms.

We describe our progress in developing the infrastructure for traceable transient measurements of pressure. Towards that end, we have built and characterized a dual diaphragm shock tube that allows us to achieve shock amplitude reproducibility of approximately 2.3 % for shocks with Mach speeds ranging from 1.26 to 1.5. In this proof-of-concept study we use our shock tube to characterize the dynamic response of photonic sensors embedded in polydimethylsiloxane (PDMS), a material of choice for soft tissue phantoms. Our results indicate that the PDMS-embedded photonic sensors response to shock evolves over tens to hundreds of microseconds time scale making it a useful system for studying transient pressures in soft tissue.

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