Inactivation of Aeromonas hydrophila and Vibrio parahaemolyticus by Curcumin-Mediated Photosensitization and Nanobubble-Ultrasonication Approaches.

The antimicrobial efficacy of novel photodynamic inactivation and nanobubble technologies was evaluated against Vibrio parahaemolyticus and Aeromonas hydrophila as two important aquatic microbial pathogens. Photodynamic inactivation results showed that LED (470 nm) and UV-A (400 nm)-activated curcumin caused a complete reduction in V. parahaemolyticus at 4 and 22 °C, and a greater than 2 log cfu/mL reduction in A. hydrophila, which was curcumin concentration-dependent (p < 0.05). Furthermore, the photodynamic approach caused a greater than 6 log cfu/mL V. parahaemolyticus reduction and more than 4 log cfu/mL of A. hydrophila reduction in aquaponic water samples (p < 0.05). Our results with the nanobubble technology showed that the nanobubbles alone did not significantly reduce bacteria (p > 0.05). However, a greater than 6 log cfu/mL A. hydrophila reduction and a greater than 3 log cfu/mL of V. parahaemolyticus reduction were achieved when nanobubble technology was combined with ultrasound (p < 0.05). The findings described in this study illustrate the potential of applying photodynamic inactivation and nanobubble-ultrasound antimicrobial approaches as alternative novel methods for inactivating fish and shellfish pathogens.

Nematic cells with quasicrystalline-patterned alignment layers.

Nematic cells with surface anchoring fields exhibiting quasicrystalline symmetry can be fabricated using linear photopolymerizable polymers and suitable optics. Using the Lebwohl-Lasher model we carry out Monte Carlo simulations of a nematic cell where the top and bottom surfaces have an anchoring field with the symmetry of a periodic approximant to a Penrose lattice. We show that the anchoring field has point topological defects, nearly all with topological charge +/-1 . Our simulations, which assume infinitely strong anchoring of the nematic to the anchoring field, show that half-integer disclination lines emerge from the point defects and either traverse the thickness of the cell for small cell thicknesses, hug the patterned surfaces for large thicknesses, or combine these behaviors for intermediate thicknesses. We show that estimates of the values of the thicknesses separating these three behaviors can be obtained using the properties of Penrose tilings.