High-resolution imaging of dielectric profiles by using a time-domain ultra wideband radar sensor

This paper describes the development of an imaging instrument that capitalizes on high-resolution phenomenon in inverse scattering using a time-domain ultra wideband (UWB) sensor. The image reconstruction algorithm that accounts for the band-limited view of the UWB data is based upon the TM-mode wave equation, the Born approximation, and the adjoint method for computing the Fréchet derivatives. The computation of the sensitivity function requires the forward propagation of the UWB wavefield, as well as the reverse propagation of the residual wavefield. The electromagnetic and adjoint fields are calculated using the finite-difference time-domain (FDTD) method, implementing the first and second orders Mur’s absorbing boundaries. The overall performance of the instrumentation system is demonstrated using computer simulations and experimental measurements. Results indicate that the equipment can reconstruct fairly complicated dielectric profiles at near millimeter resolution even with the presence of large amount of noise.     

Image analysis of macroporous polystyrene sorbents using electron spectroscopic imaging to enhance mass contrast. The architectural relationship between polymer porosity and absorption capacity

We describe the microscopical analysis of two polystyrene divinylbenzene copolymers (PS-DVB) made using 20 and 55% (v/v) DVB cross-linker respectively, in which the hydrated structure of each polymeric material solvated in water is preserved by employing very rapid freezing and low-temperature freeze-drying techniques. Using the zero-loss mode of electron spectroscopic imaging to enhance the contrast of unstained polymer sections, we introduce some novel methods for the application of computer-assisted image analysis for routine examination of polymer pore structure. We also relate these parameters to the ability of the two polymers to absorb nanometre-sized particles—neutral colloidal gold particles and cationized ferritin. Both methods will be invaluable in the structural analysis of porous polymers, but particularly for comparative analyses of macroporous sorbents.