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The diffusive dynamics of dilute dispersions of nanoparticles of diameter 200-400 nm were studied in microfabricated arrays of nanoposts using differential dynamic microscopy and single particle tracking. Posts of diameter 500 nm and height 10 μm were spaced by 1.2-10 μm on a square lattice. As the spacing between posts was decreased, the dynamics of the nanoparticles slowed. Moreover, the dynamics at all length scales were best represented by a stretched exponential rather than a simple exponential. Both the relative diffusivity and the stretching exponent decreased linearly with increased confinement and, equivalently, with decreased void volume. The slowing of the overall diffusive dynamics and the broadening distribution of nanoparticle displacements with increased confinement are consistent with the onset of dynamic heterogeneity and the approach to vitrification.

In this model of chronic valvular aortic stenosis, both Gorlin and continuity equation valve areas were flow-dependent indices of stenosis severity and demonstrated linear relations with transvalvular volume flow rate. The changes in calculated valve area that occur with changes in transvalvular volume flow should be considered when measures of valve area are used to assess the hemodynamic severity of valvular aortic stenosis.

Ordered silicon nanocavity arrays were prepared with e-beam lithography to yield systematically varied pore features and porosity (4-92%). These substrates were used to investigate the effects of substrate morphology on desorption ionization on porous silicon-mass spectrometry (DIOS-MS). Five benzylpyridinium salts, 1,2dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), and angiotensin III were used as the model molecules in the study. For substrates of the same pore depth, MS results suggested that the pore size and the interpore spacing had little impact on the laser irradiation threshold required for ionization. Instead, the laser threshold was found to be highly dependent on the overall porosity for all substrates investigatedsthe higher the porosity the lower the threshold. Moreover, the substrates with deeper pores but of similar porosity showed significantly reduced laser thresholds. This close relationship between laser threshold and substrate morphology was attributed to the thermal confinement property of porous structures. Benzylpyridinium salts were used to study molecular fragmentation tendency during desorption and ionization (D/I). The results suggested the presence of two competing D/I processes: direct laser desorption ionization (LDI) dominated for the substrates of low porosities where analytes desorbed directly from hot silicon surfaces; for highly porous substrates, the retained solvent molecules behaved as the "pseudo" matrix-assisted laser desorption/ionization (pseudo-MALDI) matrix that facilitated analyte desorption and ionization in a MALDI mode.