Nucleation barrier reconstruction via the seeding method in a lattice model with competing nucleation pathways

We study a three-species analogue of the Potts lattice gas model of nucleation from solution in a regime where partially disordered solute is a viable thermodynamic phase. Using a multicanonical sampling protocol, we compute phase diagrams for the system, from which we determine a parameter regime where the partially disordered phase is metastable almost everywhere in the temperature–fugacity plane. The resulting model shows non-trivial nucleation and growth behaviour, which we examine via multidimensional free energy calculations. We consider the applicability of the model in capturing the multi-stage nucleation mechanisms of polymorphic biominerals (e.g., CaCO3). We then quantitatively explore the kinetics of nucleation in our model using the increasingly popular “seeding” method. We compare the resulting free energy barrier heights to those obtained via explicit free energy calculations over a wide range of temperatures and fugacities, carefully considering the propagation of statistical error. We find that the ability of the “seeding” method to reproduce accurate free energy barriers is dependent on the degree of supersaturation, and severely limited by the use of a nucleation driving force ∆µ computed for bulk phases. We discuss possible reasons for this in terms of underlying kinetic assumptions, and those of classical nucleation theory. C 2016 Author(s

Data for Nucleation barrier reconstruction via the seeding method in a lattice model with competing nucleation pathways

We study a three-species analogue of the Potts Lattice Gas (PLG) model of nucleation from solution in a regime where partially disordered solute is a viable thermodynamic phase. Using a muilticanonical sampling protocol we compute phase diagrams for the system, from which we determine a parameter regime where the partially disordered phase is metastable almost everywhere in the temperature–fugacity plane. The resulting model shows non-trivial nucleation and growth behaviour, which we examine via multidimensional free energy calculations. We consider the applicability of the model in capturing the multi–stage nucleation mechanisms of polymorphic biominerals (e.g. CaCO3). We then quantitatively explore the kinetics of nucleation in our model using the increasingly popular ”seeding” method. We compare the resulting free energy barrier heights to those obtained via explicit free energy calculations over a wide range of temperatures and fugacities, carefully considering propagation of statistical error. We find that the ability of the ”seeding” method to reproduce accurate free energy barriers is dependent on the degree of supersaturation, and severely limited by the use of a nucleation driving force ∆μ computed for bulk phases. We discuss possible reasons for this in terms of underlying kinetic assumptions, and those of classical nucleation theory

Lattice models of nucleation from solution.

In this work we consider nucleation in existing and novel lattice models of particles in solution, reviewing, testing and applying the modern methodology for free energy calculation and calculation of nucleation rates based on elements of classical nucleation, reaction rate and transition path theories. We introduce a multi-component lattice model where, at low temperatures, the solute phase can form three distinct solid structures, for which we accurately map the phase diagram, discussing the relevance of the model to the study of nucleation of polymorphic minerals. By analysing multi-dimensional free energy profiles, computed via a path sampling based Monte Carlo protocol, we demonstrate that solute precipitation in the developed model can proceed via nonclassical pathways, where the formation of nuclei of unstable solute phases is followed by their transformation into the thermodynamically preferred structure. Despite the existence of nonclassical nucleation pathways, we show that the conceptual framework of classical nucleation theory provides an adequate quantitative treatment of the nucleation process in our model over a broad range of parameter space

Identification of Potentially Tolerated Fish Species by Multiplex IgE Testing of a Multinational Fish-Allergic Patient Cohort

Background: Although recent studies indicated that many fish-allergic patients may safely consume certain fish species, no clinical guidelines are available for identification of the exact species tolerated by specific patients. Objective: To investigate whether multiplex immunoglobulin E (IgE) testing reveals potentially tolerated fish through absence of IgE to parvalbumin (PV) and extracts from specific species. Methods: Sera from 263 clinically well-defined fish-allergic patients from Austria, China, Denmark, Luxembourg, Norway, and Spain were used in a research version of the ALEX 2 multiplex IgE quantification assay. Specific IgE to PVs from 10 fish species (9 bony and 1 cartilaginous), and to extracts from 7 species was quantified. The IgE signatures of individual patients and patient groups were analyzed using SPSS and R. Results: Up to 38% of the patients were negative to cod PV, the most commonly used molecule in fish allergy diagnosis. Forty-five patients (17%) tested negative to PVs but positive to the respective fish extracts, underlining the requirement for extracts for accurate diagnosis. Between 60% (Spain) and 90% (Luxembourg) of the patients were negative to PV and extracts from ray, a cartilaginous fish, indicating its potential tolerance. Up to 21% of the patients were negative to at least 1 bony fish species. Of the species analyzed, negativity to mackerel emerged as the best predictive marker of negativity to additional bony fish, such as herring and swordfish. Conclusions: Parvalbumins and extracts from multiple fish species relevant for consumption should be used in fish-allergy diagnosis, which may help identify potentially tolerated species for individual patients