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Tuning the defect configurations in nematic and smectic liquid crystalline shells
Liang, Hsin-Ling,Noh, JungHyun,Zentel, Rudolf,Rudquist, Per,Lagerwall, Jan P.F. Royal Society 2013 Philosophical transactions. Series A, Mathematical Vol.371 No.1988
<P>Thin liquid crystalline shells surrounding and surrounded by aqueous phases can be conveniently produced using a nested capillary microfluidic system, as was first demonstrated by Fernandez-Nieves <I>et al.</I> in 2007. By choosing particular combinations of stabilizers in the internal and external phases, different types of alignment, uniform or hybrid, can be ensured within the shell. Here, we investigate shells in the nematic and smectic phases under varying boundary conditions, focusing in particular on textural transformations during phase transitions, on the interaction between topological defects in the director field and inclusions in the liquid crystal (LC), and on the possibility to relocate defects within the shell by rotating the shell in the gravitational field. We demonstrate that inclusions in a shell can seed defects that cannot form in a pristine shell, adding a further means of tuning the defect configuration, and that shells in which the internal aqueous phase is not density matched with the LC will gently rearrange the internal structure upon a rotation that changes the influence of gravity. Because the defects can act as anchor points for added linker molecules, allowing self-assembly of adjacent shells, the various arrangements of defects developing in these shells and the possibility of tuning the result by modifying boundary conditions, LC phase, thickness and diameter of the shell or applying external forces make this new LC configuration very attractive.</P>
Shu-Jen Chen,Jia-Ling Chen,Wei-Chih Huang,Hsin-Liang Chen 한국화학공학회 2009 Korean Journal of Chemical Engineering Vol.26 No.2
The development of a fermentation strategy for hyaluronic acid (HA) production by Streptococcus zooepidemicus ATCC 39920 has been explored. The specific HA productivity (YP/X) was affected by the medium carbon-tonitrogen (C/N) ratio rather than the specific growth rate of cells. Accordingly, HA fermentation should be performed in a balanced medium with an optimum C/N ratio of 2 : 1 in a batch culture. To improve the performance of the batch culture, the operation conditions for the fill-and-draw culture were investigated. It was found that the timing of medium exchange is critical for successfully performing fill-and-draw operations. Since streptococcal cells at the stationary phase might lose the capacity of HA synthesis, the displacement of the medium in a fill-and-draw culture should be started at the late exponential growth phase.