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In the past ** Richard J. Sadus** has collaborated on articles with

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AbstractThe critical temperatures of some ternary siloxane mixtures are reported. The critical temperatures of binary perfluoromethylcyclohexane and siloxane mixtures were also measured. The results are compared to values calculated by solving the critical conditions from conformal solution theory using the one-fluid model, the ideal mixing equation and the Guggenheim equation of state. The agreement is good for mixtures of similar sized molecules whereas the agreement for dissimilar sized molecules is somewhat inadequate.

AbstractThe critical properties of hydrocarbon mixtures, perfluorocarbon + hydrocarbon, perfluoromethylcyclohexane + siloxane, acetone + hydrocarbon and polydimethyl siloxane mixtures have been calculated from an equation of state for hard convex bodies and from Guggenheim's equation of state for hard spheres. In general, the results of both equations agree well with experimental data.It appears, however, that taking shape factors into account (by using the hard convex body equation) does not lead to a significant improvement in the agreement between theory and experiment for the critical properties.

AbstractWe examine parallel algorithms for molecular dynamics simulations involving long-range induction interactions. The algorithms are tested by performing molecular dynamics simulations of water with an intermolecular potential that explicitly includes contributions from pair, three-body and induction interactions. Both cyclic and balanced force decomposition methods are implemented to decompose the parallelizable components of induction, pair and three-body interactions using a message passing interface. We report that more than 90% of the induction calculation, and 98% of the total calculation can be effectively parallelized. A reasonably good speedup of 15.7 times and an efficiency of 49.1% are obtained on 32 processors with the balance force decomposition algorithm.

AbstractCalculations of the critical properties of binary mixtures are reported using the Carnahan–Starling–van der Waals (CSvdW) equation of state in conjunction with the one-fluid model and the Lorentz–Berthelot combining rules for unlike interactions. The calculations are used to determine the global phase diagram of binary mixtures. A feature of the calculations is that no adjustable parameters were used in the combining rules. This means that the global phase diagram can be constructed solely in terms of experimentally measurable quantities such as the ratio of the critical temperatures and critical volumes of the component molecules. The global phase diagram accounts for almost all of the known types of fluid phase behaviour, including closed-loop liquid–liquid immiscibility. Comparisons with experimental data indicate that the global phase diagram is a good qualitative predictor of phase behaviour. Therefore, the phase behaviour type of a binary mixture can be confidently predicted solely from the ratios of critical temperatures and volumes of the pure components.

AbstractThe Gibbs ensemble algorithm is implemented to determine the vapour–liquid phase coexistence of a pure fluid interacting via a two-body Lennard–Jones+three-body Axilrod–Teller potential. The contribution of both two-body and three-body interactions are calculated exactly. The results are compared with both experiment and two-body only simulation data. The position of the vapour branch of the coexistence curve is almost unaffected by the inclusion of three-body interactions. In contrast, the liquid branch occurs at substantially lower densities compared with Lennard–Jones simulation data. However, the approach to the critical point is improved by including three-body interactions, and the estimated critical point is in good agreement with the experiment.

AbstractF1-ATPase catalyses ATP hydrolysis and converts the cellular chemical energy into mechanical rotation. The hydrolysis reaction in F1-ATPase does not follow the widely believed Michaelis–Menten mechanism. Instead, the hydrolysis mechanism behaves in an ATP-dependent manner. We develop a model for enzyme kinetics and hydrolysis cooperativity of F1-ATPase which involves the binding-state changes to the coupling catalytic reactions. The quantitative analysis and modeling suggest the existence of complex cooperative hydrolysis between three different catalysis sites of F1-ATPase. This complexity may be taken into account to resolve the arguments on the binding change mechanism in F1-ATPase.

AbstractKinesin, myosin and F1-ATPase are multi-domain molecular motors with multiple catalytic subunits. The motor mechanochemics are achieved via the conversion of ATP hydrolysis energy into forces and motions. We find that the catalysis of these molecular motors do not follow the simple Michaelis–Menten mechanism. The motor activities, such as the hydrolysis or processive rates, of kinesin, myosin and F1-ATPase have a complex ATP-dependent cooperativity. To understand this complexity in kinetics and mechanochemics, we develop a conformation correlation theory of cooperativity for the ATP-fueled motor proteins. The quantitative analysis and simulations indicate that cooperativity is induced by the conformational coupling of binding states of different subunits and prevails in the motor activities.

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