Kramers rate theory of ionization and dissociation of bound states

Calculating the microscopic dissociation rate of a bound state, such as a classical diatomic molecule, has been difficult so far. The problem was that standard theories require an energy barrier over which the bound particle (or state) escapes into the preferred low-energy state. This is not the case when the long-range repulsion responsible for the barrier is either absent or screened (as in Cooper pairs, ionized plasma, or biomolecular complexes). We solve this classical problem by accounting for entropic memory at the microscopic level. The theory predicts dissociation rates for arbitrary potentials and is successfully tested on the example of plasma, where it yields an estimate of ionization in the core of Sun in excellent agreement with experiments. In biology, the new theory accounts for crowding in receptor-ligand kinetics and protein aggregation

Spinodal-assisted crystallization in polymer melts

Recent experiments in some polymer melts quenched below the melting temperature have reported spinodal kinetics in small-angle x-ray scattering before the emergence of a crystalline structure. To explain these observations we propose that the coupling between density and chain conformation induces a liquid-liquid binodal within the equilibrium liquid-crystalline solid coexistence region. A simple phenomenological theory is developed to illustrate this idea, and several experimentally testable consequences are discussed. Shear is shown to enhance the kinetic role of the hidden binodal

Exploring the Influence of Family on Adolescents’ Seafood Consumption Choices

Seafood in the adolescent diet has many benefits, yet a number of adolescents do not consume the recommended levels. Despite this the consumption of seafood by younger consumers has received scant attention in the extant literature. Previous studies on adolescents’ food-related behaviour tend to focus on general choice mechanisms or perceptions of food and mainly relate to fruit and vegetable intake. The present study seeks to address this gap through investigating the impact of family upon the consumption of seafood by younger consumers through exploring adolescents’ attitudes and behaviour in regard to eating seafood. Utilising an exploratory qualitative methodology, seven focus groups of adolescents aged 13–19 years were conducted at two schools in South-West England. Discussions covered a range of issues related to adolescent seafood consumption. The use of thematic content analysis found that the family, and parents in particular, exert high levels of influence over adolescents’ consumption of seafood both at home and when dining out. The parent who does the shopping and cooking has the greatest role. Sibling preferences and dietary choices also influence whether seafood is served in the home. Of value to researchers and management are the insights gleaned into the influences on adolescents’ attitudes toward and behaviour in regard to eating seafood. In particular encouraging seafood consumption will rely upon interventions aimed at both parents and children and need to take into account adolescents’ diet and lifestyle preferences, while also acknowledging the influence of peers and the school food environment

Ten Years After: An ‘Austerity Audit’ of Services and Living Conditions for People Living with HIV in the UK, a Decade after the Financial Crisis

Cite as: HIV Psychosocial Network (2018). Ten Years After: An ‘Austerity Audit’ of Services and Living Conditions for People Living with HIV in the UK, a Decade after the Financial Crisis

Parallel Excluded Volume Tempering for Polymer Melts

We have developed a technique to accelerate the acquisition of effectively uncorrelated configurations for off-lattice models of dense polymer melts which makes use of both parallel tempering and large scale Monte Carlo moves. The method is based upon simulating a set of systems in parallel, each of which has a slightly different repulsive core potential, such that a thermodynamic path from full excluded volume to an ideal gas of random walks is generated. While each system is run with standard stochastic dynamics, resulting in an NVT ensemble, we implement the parallel tempering through stochastic swaps between the configurations of adjacent potentials, and the large scale Monte Carlo moves through attempted pivot and translation moves which reach a realistic acceptance probability as the limit of the ideal gas of random walks is approached. Compared to pure stochastic dynamics, this results in an increased efficiency even for a system of chains as short as $N = 60$ monomers, however at this chain length the large scale Monte Carlo moves were ineffective. For even longer chains the speedup becomes substantial, as observed from preliminary data for $N = 200$