Chromonic liquid crystals and packing configurations of bacteriophage viruses

We study equilibrium configurations of hexagonal columnar liquid crystals in the context of characterizing packing structures of bacteriophage viruses in a protein capsid. These are viruses that infect bacteria and are currently the focus of intense research efforts, with the goal of finding new therapies for bacteria-resistant antibiotics. The energy that we propose consists of the Oseen–Frank free energy of nematic liquid crystals that penalizes bending of the columnar directions, in addition to the cross-sectional elastic energy accounting for distortions of the transverse hexagonal structure; we also consider the isotropic contribution of the core and the energy of the unknown interface between the outer ordered region of the capsid and the inner disordered core. The problem becomes of free boundary type, with constraints. We show that the concentric, azimuthal, spool-like configuration is the absolute minimizer. Moreover, we present examples of toroidal structures formed by DNA in free solution and compare them with the analogous ones occurring in experiments with other types of lyotropic liquid crystals, such as food dyes and additives. This article is part of the theme issue ‘Topics in mathematical design of complex materials’.

Punching above its weight: life cycle energy accounting and environmental assessment of vanadium microalloying in reinforcement bar steel

High-strength-low-alloy reinforcement bar steels prepared by vanadium microalloying methods have the potential to dramatically reduce the embodied energy and carbon footprint of buildings.

The critical role of advanced sustainability assessment tools in enhancing the real-world application of biofuels

Sustainability has become of paramount importance in the biofuel industry. Accordingly, various ‎sustainability assessment schemes such as emergy analysis, techno-economic analysis, life ‎cycle ‎assessment, energy accounting, and exergy analysis and its extensions (exergoeconomic, ‎exergoenvironmental, and ‎exergoeconoenvironmental analyses) are being employed increasingly for decision-‎making on biofuel production and consumption systems. In this opinion paper, after classifying ‎and describing biofuel generations, the developed sustainability assessment tools are critically ‎explained, and their pros and cons are discussed. Overall, among the various sustainability assessment approaches introduced so far, exergy-based methods appear to be ‎the most promising tools for developing ‎sustainable biofuel systems. This can be attributed to the fact that the exergy ‎concept is deeply ‎rooted in the well-defined principles of thermodynamics.‎