Influenza: From zoonosis to pandemic

Global surveillance and advances in vaccine technology are essential to answer the threat of influenza pandemics http://ow.ly/Yt3e

Lehmann rotation of cholesteric droplets subjected to a temperature gradient: role of the concentration of chiral molecules

International audienceWe present a systematic study of the Lehmann rotation of cholesteric droplets subjected to a temperature gradient when the concentration of chiral molecules is changed. The liquid crystal chosen is an eutectic mixture of 8CB and 8OCB doped with a small amount of the chiral molecule R811. The angular velocity of the droplets strongly depend on their size and on the concentration of chiral molecules. The Lehmann coefficient is estimated by using three different methods. Our results are consistent with a Lehmann coefficient proportional to the concentration of chiral molecules. We additionally show the existence of a critical size of the droplets below which they change texture and stop rotating

Dynamics of cholesteric structures in an electric field

Motivated by Lehmann-like rotation phenomena in cholesteric drops we study the transverse drift of two types of cholesteric fingers, which form rotating spirals in thin layers of cholesteric liquid crystal in an ac or dc electric field. We show that electrohydrodynamic effects induced by Carr-Helfrich charge separation or flexoelectric charge generation can describe the drift of cholesteric fingers. We argue that the observed Lehmann-like phenomena can be understood on the same basis.Comment: 4 pages, 4 figures, submitted to PR

Well-posedness of the Ericksen-Leslie system

In this paper, we prove the local well-posedness of the Ericksen-Leslie system, and the global well-posednss for small initial data under the physical constrain condition on the Leslie coefficients, which ensures that the energy of the system is dissipated. Instead of the Ginzburg-Landau approximation, we construct an approximate system with the dissipated energy based on a new formulation of the system.Comment: 16 page

Regulation of Homer and group I metabotropic glutamate receptors by nicotine

The present study focuses on the nicotine-induced modulation of mRNA and protein expression of a number of genes involved in glutamatergic synaptic transmission in rat brain over different time periods of exposure. A subchronic (3 days) but not the chronic (7 or 14 days) administration of nicotine resulted in the up-regulation of Homer2a/b mRNA in the amygdala while in the ventral tegmental area (VTA) no change in expression of either Homer2a/b or Homer1b/c was observed. Although the increase in Homer2a/b mRNA was not translated into the protein level in the amygdala, a slight but significant up-regulation of Homer1b/c protein was observed in the same region at day 3. Both Homer forms were up-regulated at the protein level in the VTA at day 3. In the nucleus accumbens, 14 days of nicotine treatment up-regulated mRNA of Homer2b/c by 68.2% (P < 0.05), while the short form Homer1a gene was down-regulated by 65.0% at day 3 (P < 0.05). In regard to other components of the glutamatergic signalling, we identified an acute and intermittent increase in the mRNA and protein levels of mGluR1 and mGluR5 in the amygdala. In the VTA, however, the effects of nicotine on mGluR mRNA expression were long-lasting but rather specific to mGluR1. Nevertheless, mGluR1 protein levels in the VTA area were up-regulated only at day 3, as in the amygdala. These data provide further evidence for the involvement of nicotine in the glutamatergic neuronal synaptic activity in vivo, suggesting a role for the newly identified Homer proteins in this paradigm

Energy Dissipation and Regularity for a Coupled Navier-Stokes and Q-Tensor System

We study a complex non-newtonian fluid that models the flow of nematic liquid crystals. The fluid is described by a system that couples a forced Navier-Stokes system with a parabolic-type system. We prove the existence of global weak solutions in dimensions two and three. We show the existence of a Lyapunov functional for the smooth solutions of the coupled system and use the cancellations that allow its existence to prove higher global regularity, in dimension two. We also show the weak-strong uniqueness in dimension two

Blow up criterion for compressible nematic liquid crystal flows in dimension three

In this paper, we consider the short time strong solution to a simplified hydrodynamic flow modeling the compressible, nematic liquid crystal materials in dimension three. We establish a criterion for possible breakdown of such solutions at finite time in terms of the temporal integral of both the maximum norm of the deformation tensor of velocity gradient and the square of maximum norm of gradient of liquid crystal director field.Comment: 22 page

Hydrodynamics of domain growth in nematic liquid crystals

We study the growth of aligned domains in nematic liquid crystals. Results are obtained solving the Beris-Edwards equations of motion using the lattice Boltzmann approach. Spatial anisotropy in the domain growth is shown to be a consequence of the flow induced by the changing order parameter field (backflow). The generalization of the results to the growth of a cylindrical domain, which involves the dynamics of a defect ring, is discussed.Comment: 12 revtex-style pages, including 12 figures; small changes before publicatio

Global weak solution and large-time behavior for the compressible flow of liquid crystals

The three-dimensional equations for the compressible flow of liquid crystals are considered. An initial-boundary value problem is studied in a bounded domain with large data. The existence and large-time behavior of a global weak solution are established through a three-level approximation, energy estimates, and weak convergence for the adiabatic exponent $\gamma>\frac32$