SHELF LIFE OF THAWED CRUSTACEANS TREATED WITH SULPHITES

The quality of fish and fish products is closely related to their freshness. Aim of this research was to evaluate the shelf life of thawed crustaceans (Aristeomorpha foliacea and Nefrops norvegicus) which had been treated with sulphites and frozen on board. Organoleptic characteristics and microbiological and chemical parameters were judged favourably up to day 6 and 7 for the shrimps and Norway lobsters, respectively

Simple Fluids with Complex Phase Behavior

We find that a system of particles interacting through a simple isotropic potential with a softened core is able to exhibit a rich phase behavior including: a liquid-liquid phase transition in the supercooled phase, as has been suggested for water; a gas-liquid-liquid triple point; a freezing line with anomalous reentrant behavior. The essential ingredient leading to these features resides in that the potential investigated gives origin to two effective core radii.Comment: 7 pages including 3 eps figures + 1 jpeg figur

Effective interactions in molecular dynamics simulations of lysozyme solutions

In this article we explore a problem of effective interactions between two rotationally restrained lysozyme molecules forming a crystal contact in aqueous solution. We perform non-equilibrium molecular dynamics simulations in order to estimate the interaction energy as a function of the distance between the two proteins obtained from direct application of the Jarzynski equality (JE), and compare it with that calculated by means of another non-equilibrium approach (Forward-Reverse method) and constrained force methods. The performance of the JE equality when applied to solvated protein interactions is discussed. All of the equilibrium and non-equilibrium methods show clear evidence that the potentials of mean force (PMF) are short-ranged, do not exceed few kTs, and that there is an accumulation of anions in the presence of hydrophobic surfaces

Adsorption of binary polymer mixtures with different topology on a wall

We consider a binary mixture of two polymers with different architecture, consisting of linear and cyclic chains. We study this system by performing extensive molecular dynamics computer simulations of bead-spring models, which possess the open-chain and loop topology. The system is confined between two walls, and we consider both the case of attractive- and repulsive polymer-wall interactions. By changing the chain length of the two polymers so as to encompass two regimes with low and high degree of polymerization, we show the effect on the structural properties at the interface. Our results provide some physical insight on the competition between polymer architecture and chain length in determining the surface adsorption. 2000 MSC: 41A05, 41A10, 65D05, 65D17, Keywords: Adsorption, Polymer architecture, Wall-fluid potentia

Self-Assembled Structures of Colloidal Dimers and Disks on a Spherical Surface

We study self-assembly on a spherical surface of a model for a binary mixture of amphiphilic dimers in the presence of guest particles via Monte Carlo (MC) computer simulation. All particles had a hard core, but one monomer of the dimer also interacted with the guest particle by means of a short-range attractive potential. We observed the formation of aggregates of various shapes as a function of the composition of the mixture and of the size of guest particles. Our MC simulations are a further step towards a microscopic understanding of experiments on colloidal aggregation over curved surfaces, such as oil droplets

Theory and equation of state of two-component nonadditive hard-disks: an application in the colloidal regime

22 pags., 14 figs.We use theoretical and Monte Carlo computer simulations to study thermodynamic and structural properties of a binary mixture of nonadditive hard-disks. The nonadditivity parameter is set to assume negative values so as to favour heterocoordination between the two species. The theoretical approaches include the Rescaled Virial Expansion Equation of State, which is based on the knowledge of the virial coefficients of the mixture, and the Rogers-Young Integral-Equation Theory. The comparison with Monte Carlo data shows that the microscopic theory is able to provide a reliable prediction of both the equation of state and the radial distribution functions of the system. These results are of interest because binary mixtures of colloidal particles adsorbed at the interface exhibit a wide range of self-assembly phenomena, and achieving of a reliable fluid state theory for a simple model of these systems is an essential milestone to be able to understand their nature.G. P. acknowledges the South African Center for High Performance Computing (CHPC) and Dr A. Lopis for assistance and granting access to computational resources under the allocation MATS0887. E.L. acknowledges support from the Agencia Estatal de Investigación and Fondo Europeo de Desarrollo Regional (FEDER) under grant No. PID2020-115722GB-C21

Thermodynamics of a stochastic three level elevator model

We study the thermodynamic properties of a single particle occupying one of three available energy levels in a non-equilibrium regime. The particle is thermally coupled to a classical Maxwell-Boltzmann thermal reservoir and can jump among the available levels by exchanging energy with the heat bath. The bottom and middle energy levels are simultaneously raised at a given rate regardless of particle occupation, but keeping the energy gaps among the three levels fixed. We explicitly calculate the work, heat and entropy production rates, and the classical efficiency. We also consider the case of a Bose-Einstein thermal reservoir and provide explicit expressions for the non-equilibrium, steady-state probabilities