Twist-Bend Nematic Phase from the Landau-de Gennes Perspective.

Generalized Landau-de Gennes theory is proposed that comprehensively explains currently available experimental data for the heliconical twist-bend nematic (N) phase observed in liquid crystalline systems of chemically bent-core-like molecules. A bifurcation analysis gives insight into possible structures that the model can predict and guides in the numerical analysis of relative stability of the isotropic (I), uniaxial nematic (N), and twist-bend nematic phases. An estimate of constitutive parameters of the model from temperature variation of the nematic order parameter and the Frank elastic constants in the nematic phase enables us to demonstrate quantitative agreement between the calculated and experimentally determined temperature dependence of the pitch and conical angle in N.

Role of molecular bend angle and biaxiality in the stabilization of the twist-bend nematic phase.

What are the prerequisites for acquiring a stable twist-bend nematic phase (NTB)? Addressing this question has led to the synthesis of a vast number of new compounds, concluding each time that the molecule's shape is one of the predominant factors. Inspired by the expanding knowledge of different achiral bent-shaped molecules forming a twist-bend nematic phase, we reinvestigate the interplay between a molecule's bend angle and a molecule's arms molecular biaxiality. Employing our previously developed generalized mean-field model, we explore more obtuse bend angles.

Polydactyly suggesting local husbandry of Pre-Columbian camelids: A case from Castillo de Huarmey archaeological site, northern coast of Peru.

Three camelid metapodials with polydactyly (additional digits) were found at the Wari culture archaeological site (dated to the Middle Horizon) of Castillo de Huarmey. The anomalous bones were excavated among numerous remains, and presumably represent animals that were sacrificed within the principal mortuary mausoleum. The bones derive from at least two individuals.

Twist-bend nematic phases of bent-shaped biaxial molecules.

How can a change in molecular structure affect the relative stability and structural properties of the twist-bend nematic phase (NTB)? Here we extend the mean-field model(1) (C. Greco, G. R.

Phase Behavior and Dynamics of the Liquid Crystal 4'-butyl-4-(2-methylbutoxy)azoxybenzene (4ABO5*).

The results of dielectric relaxation spectroscopy and polarizing microscope observation of the 4'-butyl-4-(2-methylbutoxy)azoxybenzene (abbreviated as 4ABO5*) are presented. Numerical analysis of the dielectric spectra results points to complex dynamics of 4ABO5* molecules in isotropic, cholesteric, and crystalline phases. Two well-separated maxima on the imaginary part of dielectric permittivity and the third low frequency relaxation process, hidden in the conductivity region, were detected and described in cholesteric and crystalline phases.