Hydrodynamics of topological defects in nematic liquid crystals

We show that back-flow, the coupling between the order parameter and the velocity fields, has a significant effect on the motion of defects in nematic liquid crystals. In particular the defect speed can depend strongly on the topological strength in two dimensions and on the sense of rotation of the director about the core in three dimensions.Comment: 4 pages including two figure

Phase Ordering in Nematic Liquid Crystals

We study the kinetics of the nematic-isotropic transition in a two-dimensional liquid crystal by using a lattice Boltzmann scheme that couples the tensor order parameter and the flow consistently. Unlike in previous studies, we find the time dependences of the correlation function, energy density, and the number of topological defects obey dynamic scaling laws with growth exponents that, within the numerical uncertainties, agree with the value 1/2 expected from simple dimensional analysis. We find that these values are not altered by the hydrodynamic flow. In addition, by examining shallow quenches, we find that the presence of orientational disorder can inhibit amplitude ordering.Comment: 21 pages, 14 eps figures, revte

Modelling nematohydrodynamics in liquid crystal devices

We formulate a lattice Boltzmann algorithm which solves the hydrodynamic equations of motion for nematic liquid crystals. The applicability of the approach is demonstrated by presenting results for two liquid crystal devices where flow has an important role to play in the switching.Comment: 6 pages including 5 figure

Lattice Boltzmann Algorithm for three-dimensional liquid crystal hydrodynamics

We describe a lattice Boltzmann algorithm to simulate liquid crystal hydrodynamics in three dimensions. The equations of motion are written in terms of a tensor order parameter. This allows both the isotropic and the nematic phases to be considered. Backflow effects and the hydrodynamics of topological defects are naturally included in the simulations, as are viscoelastic effects such as shear-thinning and shear-banding. We describe the implementation of velocity boundary conditions and show that the algorithm can be used to describe optical bounce in twisted nematic devices and secondary flow in sheared nematics with an imposed twist.Comment: 12 pages, 3 figure

Elastic response of a nematic liquid crystal to an immersed nanowire

We study the immersion of a ferromagnetic nanowire within a nematic liquid crystal using a lattice Boltzmann algorithm to solve the full three-dimensional equations of hydrodynamics. We present an algorithm for including a moving boundary, to simulate a nanowire, in a lattice Boltzmann simulation. The nematic imposes a torque on a wire that increases linearly with the angle between the wire and the equilibrium direction of the director field. By rotation of these nanowires, one can determine the elastic constants of the nematic.Comment: 10 pages, 8 figure

Numerical calculations of the phase diagram of cubic blue phases in cholesteric liquid crystals

We study the static properties of cubic blue phases by numerically minimising the three-dimensional, Landau-de Gennes free energy for a cholesteric liquid crystal close to the isotropic-cholesteric phase transition. Thus we are able to refine the powerful but approximate, semi-analytic frameworks that have been used previously. We obtain the equilibrium phase diagram and discuss it in relation to previous results. We find that the value of the chirality above which blue phases appear is shifted by 20% (towards experimentally more accessible regions) with respect to previous estimates. We also find that the region of stability of the O5 structure -- which has not been observed experimentally -- shrinks, while that of BP I (O8-) increases thus giving the correct order of appearance of blue phases at small chirality. We also study the approach to equilibrium starting from the infinite chirality solutions and we find that in some cases the disclination network has to assemble during the equilibration. In these situations disclinations are formed via the merging of isolated aligned defects.Comment: 16 pages, 5 figures. Accepted for publication in Phys. Rev.

Federal Agency Efforts to Advance Media Literacy in Substance Abuse Prevention

This article describes and reflects upon efforts to generate greater support for media literacy and critical thinking within the strategies and programs of the Federal government, primarily in agencies with an interest in youth substance abuse prevention. Additionally, some of the inherent challenges and obstacles that impacted the ability to expand these efforts are discussed

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

A Kingdom Project. Developing formational supervision: a critical assessment of training offered to supervisors of candidates for ministry within the Church of Scotland

The supervision of students for ministry is of primary importance for the Church today. In a context where religion is becoming increasingly privatised and the Church increasingly marginalised, not only are there fewer candidates presenting for ministry, and fewer ministers, the challenges facing these ministers become ever more complex. Although the study of theology is basic to the exercise of ministry, the skills for ministry are learned on placement, where a student engages in the practice of ministry supervised by an experienced and trained minister. It is from this supervisor that the trainee minister learns how to deal with the complexities of ministry today. It follows, therefore, that the training given to such supervisors must be developed to take account of the changing role of ministry. The Church of Scotland has an intensive training course for these supervisors whom I will refer to as ‘formational supervisors’. This thesis aims to evaluate this training to ascertain the extent to which it equips formational supervisors for the task. To do this, I interviewed six formational supervisors and the six probationer ministers on placement in their congregations to determine the extent to which supervisory practice was sharpened and enhanced by the Church of Scotland’s current training programme, where any weaknesses lay, and, therefore, whether the training was fit for purpose. The results of my research show that the training offered is very good but could be excellent. I outline the strengths and weaknesses of the training as it is currently configured and suggest areas for development. I make ten recommendations for improvements to the training. I also identify the characteristics of the formational supervisor which sets this type of supervision apart from pastoral or clinical supervision. This is significant in enabling appropriate training in formational supervision. The results of the research, while being of importance for the training of formational supervisors of ministry students in the Church of Scotland, have wider application. These results would also be helpful for reflecting on training in other churches and could be developed for the training of formational supervisors in any discipline