Effects of parylene-C photooxidation on serum-assisted glial and neuronal patterning.

The increasing use of patterned neural networks in multielectrode arrays and similar devices drives the constant development and evaluation of new biomaterials. Recently, we presented a promising technique to guide neurons and glia reliably and effectively. Parylene-C, a common hydrophobic polymer, was photolithographically patterned on silicon oxide (SiO(2)) and subsequently activated via immersion in serum. In this article, we explore the effects of ultraviolet (UV)-induced oxidation on parylene's ability to pattern neurons and glia. We exposed parylene-C stripe patterns to increasing levels of UV radiation and found a dose-dependent reduction in the total mass of patterned cells, as well as a gradual loss of glial and neuronal conformity to the patterns. In contrast, nonirradiated patterns had superior patterning results and increased presence of cells. The reduced cell adhesion and patterning after the formation of aldehyde and carboxyl groups on UV-radiated parylene-C supports our hypothesis that cell adhesion and growth on parylene is facilitated by hydrophobic adsorption of serum proteins. We conclude that unlike other cell patterning schemes, our technique does not rely on photooxidation of the polymer. Nonetheless, the precise control of oxygenated groups on parylene could pave the way for the differential binding of proteins and other molecules on the surface, aiding in the adhesion of alternative cell types. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res, 2010.

Multiply conditioned analyses of stratification in highly swirling methane/air flames

The effects of stratification on a series of highly swirling turbulent flames under globally lean conditions (φg=0.75) are investigated using a new high-spatial resolution multi-scalar dataset. This dataset features two key properties: high spatial resolution which approaches the 60 micron optical limit of the measurement system, and a wavelet oversampling methodology which significantly reduces the influence of noise. Furthermore, the very large number of realizations (30,000) acquired in the stratified cases permits statistically significant results to be obtained even after aggressive conditioning is applied. Data are doubly conditioned on equivalence ratio and the degree of stratification across the flame in each instantaneous realization. The influence of stoichiometry is limited by conditioning on the equivalence ratio at the location of peak CO mass fraction, which is shown to be a good surrogate for the location of peak heat release rate, while the stratification is quantified using a linear gradient in equivalence ratio across the instantaneous flame front. This advanced conditioning enables robust comparisons with the baseline lean premixed flame. Species mass fractions of both carbon monoxide and hydrogen are increased in temperature space under stratified conditions. Stratification is also shown to significantly increase thermal gradients, yet the derived three-dimensional flame surface density is shown to be relatively insensitive to stratification. Whilst the presence of instantaneous stratification broadens the curvature distribution relative to the premixed case, the degree of broadening is not significantly influenced by the range of global stratification ratios examined in this study. © 2012 The Combustion Institute.