Monte Carlo Methods for Estimating Interfacial Free Energies and Line Tensions

Excess contributions to the free energy due to interfaces occur for many problems encountered in the statistical physics of condensed matter when coexistence between different phases is possible (e.g. wetting phenomena, nucleation, crystal growth, etc.). This article reviews two methods to estimate both interfacial free energies and line tensions by Monte Carlo simulations of simple models, (e.g. the Ising model, a symmetrical binary Lennard-Jones fluid exhibiting a miscibility gap, and a simple Lennard-Jones fluid). One method is based on thermodynamic integration. This method is useful to study flat and inclined interfaces for Ising lattices, allowing also the estimation of line tensions of three-phase contact lines, when the interfaces meet walls (where "surface fields" may act). A generalization to off-lattice systems is described as well. The second method is based on the sampling of the order parameter distribution of the system throughout the two-phase coexistence region of the model. Both the interface free energies of flat interfaces and of (spherical or cylindrical) droplets (or bubbles) can be estimated, including also systems with walls, where sphere-cap shaped wall-attached droplets occur. The curvature-dependence of the interfacial free energy is discussed, and estimates for the line tensions are compared to results from the thermodynamic integration method. Basic limitations of all these methods are critically discussed, and an outlook on other approaches is given

Ancient hybridizations among the ancestral genomes of bread wheat.

The allohexaploid bread wheat genome consists of three closely related subgenomes (A, B, and D), but a clear understanding of their phylogenetic history has been lacking. We used genome assemblies of bread wheat and five diploid relatives to analyze genome-wide samples of gene trees, as well as to estimate evolutionary relatedness and divergence times. We show that the A and B genomes diverged from a common ancestor ~7 million years ago and that these genomes gave rise to the D genome through homoploid hybrid speciation 1 to 2 million years later. Our findings imply that the present-day bread wheat genome is a product of multiple rounds of hybrid speciation (homoploid and polyploid) and lay the foundation for a new framework for understanding the wheat genome as a multilevel phylogenetic mosaic

How to look good (nearly) naked: the performative regulation of the swimmer's body

This article explores the discursive construction, regulation and performance of the body in the context of the swimming pool. The near-naked state of the swimmers body presents a potential threat to the interaction order, insofar as social encounters may be misconstrued as sexual, and so rituals are enacted to create a `civilized definition of the situation. The term `performative regulation is introduced to theorize this process, as a synergy of the symbolic interactionist models of dramaturgy (Goffman) and negotiated order (Strauss) and the post-structuralist concept of disciplinary power (Foucault). The regulation and representation of the swimmers body can be understood as mutually constitutive mechanisms, enforced by the pool-as-institution but enacted through the embodied practices of individual actors in the pool-as-interaction. Crossleys notion of reflexive body techniques is applied to interpret this dualistic process in relation to communicative gestures and facework rituals, which implicates both individual and social bodies in the somatization of the interaction order