Biharmonic pattern selection

A new model to describe fractal growth is discussed which includes effects due to long-range coupling between displacements $u$. The model is based on the biharmonic equation $\nabla^{4}u =0$ in two-dimensional isotropic defect-free media as follows from the Kuramoto-Sivashinsky equation for pattern formation -or, alternatively, from the theory of elasticity. As a difference with Laplacian and Poisson growth models, in the new model the Laplacian of $u$ is neither zero nor proportional to $u$. Its discretization allows to reproduce a transition from dense to multibranched growth at a point in which the growth velocity exhibits a minimum similarly to what occurs within Poisson growth in planar geometry. Furthermore, in circular geometry the transition point is estimated for the simplest case from the relation $r_{\ell}\approx L/e^{1/2}$ such that the trajectories become stable at the growing surfaces in a continuous limit. Hence, within the biharmonic growth model, this transition depends only on the system size $L$ and occurs approximately at a distance $60 \%$ far from a central seed particle. The influence of biharmonic patterns on the growth probability for each lattice site is also analysed.Comment: To appear in Phys. Rev. E. Copies upon request to [email protected]

Automated Structure Solution with the PHENIX Suite

Significant time and effort are often required to solve and complete a macromolecular crystal structure. The development of automated computational methods for the analysis, solution and completion of crystallographic structures has the potential to produce minimally biased models in a short time without the need for manual intervention. The PHENIX software suite is a highly automated system for macromolecular structure determination that can rapidly arrive at an initial partial model of a structure without significant human intervention, given moderate resolution and good quality data. This achievement has been made possible by the development of new algorithms for structure determination, maximum-likelihood molecular replacement (PHASER), heavy-atom search (HySS), template and pattern-based automated model-building (RESOLVE, TEXTAL), automated macromolecular refinement (phenix.refine), and iterative model-building, density modification and refinement that can operate at moderate resolution (RESOLVE, AutoBuild). These algorithms are based on a highly integrated and comprehensive set of crystallographic libraries that have been built and made available to the community. The algorithms are tightly linked and made easily accessible to users through the PHENIX Wizards and the PHENIX GUI

Fear appeals in anti-smoking advertising : how important is self-efficacy?

This is an Accepted Manuscript of an article published by Taylor & Francis in Journal of Marketing Management on 11 October 2012, available online at: http://www.tandfonline.com/doi/abs/10.1080/0267257X.2012.715092Fear appeals are frequently used in anti-smoking advertising. The evidence on the effectiveness of fear appeals is mixed, and in some studies strong fear appeals have been found to reinforce the undesirable behaviour. Individual self-efficacy may play a role in moderating the effects of fear appeals. In advertising contexts where the intention was to encourage socially desirable behaviours, it has been shown that greater self-efficacy is associated with a more positive response to fear appeals. Similarly, in such contexts, the perceived ethicality of a fear-appeal advertisement appears to be positively related to self-efficacy. The purpose of this article is to examine the relationship between self-efficacy, perceived ethicality, and the impact of advertising on behavioural intentions in a context where the aim is to discourage undesirable behaviour, namely anti-smoking advertising. Questionnaire data were gathered from 434 respondents in London, England. Respondents with higher reported self-efficacy were found to have more favourable views of the ethicality of fear-appeal advertising, more positive attitudes towards the advertising, and stronger intentions to quit smoking. It is recommended that when using fear appeals in advertising to discourage undesirable behaviour, advertisers should incorporate messages designed to enhance self-efficacy.Peer reviewe