Modelling the phase and chemical equilibria of aqueous solutions of alkanolamines and carbon dioxide using the SAFT-γ SW group contribution approach

p>All computational data for figures presented in the publication/p

Development of intermolecular potential models for electrolyte solutions using an electrolyte SAFT-VR Mie equation of state

We present a theoretical framework and parameterisation of intermolecular potentials for aqueous electrolyte solutions using the statistical associating fluid theory based on the Mie interaction potential (SAFT-VR Mie), coupled with the primitive, non-restricted mean-spherical approximation (MSA) for electrolytes. In common with other SAFT approaches, water is modelled as a spherical molecule with four off-centre association sites to represent the hydrogen-bonding interactions; the repulsive and dispersive interactions between the molecular cores are represented with a potential of the Mie (generalised Lennard-Jones) form. The ionic species are modelled as fully dissociated, and each ion is treated as spherical: Coulombic ion–ion interactions are included at the centre of a Mie core; the ion–water interactions are also modelled with a Mie potential without an explicit treatment of ion–dipole interaction. A Born contribution to the Helmholtz free energy of the system is included to account for the process of charging the ions in the aqueous dielectric medium. The parameterisation of the ion potential models is simplified by representing the ion–ion dispersive interaction energies with a modified version of the London theory for the unlike attractions. By combining the Shannon estimates of the size of the ionic species with the Born cavity size reported by Rashin and Honig, the parameterisation of the model is reduced to the determination of a single ion–solvent attractive interaction parameter. The resulting SAFT-VRE Mie parameter sets allow one to accurately reproduce the densities, vapour pressures, and osmotic coefficients for a broad variety of aqueous electrolyte solutions; the activity coefficients of the ions, which are not used in the parameterisation of the models, are also found to be in good agreement with the experimental data. The models are shown to be reliable beyond the molality range considered during parameter estimation. The inclusion of the Born free-energy contribution, together with appropriate estimates for the size of the ionic cavity, allows for accurate predictions of the Gibbs free energy of solvation of the ionic species considered. The solubility limits are also predicted for a number of salts; in cases where reliable reference data are available the predictions are in good agreement with experiment

Unknown Unknowns or: How I Learned to Stop Worrying and Love the Balloon!

Produced in response to the Critical Kits symposium on 30th November 2016 which was organised by Redock, a community arts collective, at which creatives and makers dissected notions of critical kits with regard to their own practice. In this context ‘Critical Kits’ was used as a shorthand for all the issues around documenting participatory artistic practice that uses technology of various kinds, not just projects that use kits. Written in collaboration with Jonathan Spencer, and due for publication by Torque later in the year as part of the book Critical Kits which presents an edited series of critical reviews of design and artistic practice, the article reflects on our practice and experiences with the OLO project and the Gym Jams event, particularly with regard to integrating technologies into participatory events / artworks and cross disciplinary collaboration between designers, artists and makers. It examines and critiques our own relationship to the project, expectations versus reality, the ambition of the project, the processes involved and the intersection of art and public engagement. These findings can be used by practitioners to inform future works and collaborations as part of an iterative process

Analysis of protein acylation.

Proteins can be acylated with a variety of fatty acids attached by different covalent bonds, influencing, among other things, their function and intracellular localization. This unit describes methods to analyze protein acylation, both levels of acylation and also the identification of the fatty acid and the type of bond present in the protein of interest. Protocols are provided for metabolic labeling of proteins with tritiated fatty acids, for exploitation of the differential sensitivity to cleavage of different types of bonds, in order to distinguish between them, and for thin-layer chromatography to separate and identify the fatty acids associated with proteins.Accepted versio

Africa Is Much Bigger Than You Think It Is

Historically, Africa has tended to be misrepresented in maps. In the commonly used Mercator method of mapping a sphere (the Earth) onto a at plane (a map), countries further away from the equator are distorted and enlarged. Consequently, Africa is diminished and presented as smaller than it actually is. This work seeks to correct this misrepresentation by showing the continent in relation to something we associate as being large - the Moon. Both images are to the same scale and sized correctly relative to each other

Group contribution methodology based on the statistical associating fluid theory for heteronuclear molecules formed from Mie segments

A generalization of the recent version of the statistical associating fluid theory for variable range Mie potentials [Lafitte et al., J. Chem. Phys. 139, 154504 (2013)] is formulated within the framework of a group contribution approach (SAFT-γ Mie). Molecules are represented as comprising distinct functional (chemical) groups based on a fused heteronuclear molecular model, where the interactions between segments are described with the Mie (generalized Lennard-Jonesium) potential of variable attractive and repulsive range. A key feature of the new theory is the accurate description of the monomeric group-group interactions by application of a high-temperature perturbation expansion up to third order. The capabilities of the SAFT-γ Mie approach are exemplified by studying the thermodynamic properties of two chemical families, the n-alkanes and the n-alkyl esters, by developing parameters for the methyl, methylene, and carboxylate functional groups (CH3, CH2, and COO). The approach is shown to describe accurately the fluid-phase behavior of the compounds considered with absolute average deviations of 1.20% and 0.42% for the vapor pressure and saturated liquid density, respectively, which represents a clear improvement over other existing SAFT-based group contribution approaches. The use of Mie potentials to describe the group-group interaction is shown to allow accurate simultaneous descriptions of the fluid-phase behavior and second-order thermodynamic derivative properties of the pure fluids based on a single set of group parameters. Furthermore, the application of the perturbation expansion to third order for the description of the reference monomeric fluid improves the predictions of the theory for the fluid-phase behavior of pure components in the near-critical region. The predictive capabilities of the approach stem from its formulation within a group-contribution formalism: predictions of the fluid-phase behavior and thermodynamic derivative properties of compounds not included in the development of group parameters are demonstrated. The performance of the theory is also critically assessed with predictions of the fluid-phase behavior (vapor-liquid and liquid-liquid equilibria) and excess thermodynamic properties of a variety of binary mixtures, including polymer solutions, where very good agreement with the experimental data is seen, without the need for adjustable mixture parameters