Single-Site Local-Density Potentials for the Mesoscopic Representation of Water Based on the SAFT-VR Mie Equation of State.

In this article, we present three mesoscopic models for water. All three models make use of local density-dependent interaction potentials, as employed within the Pagonabarraga-Frenkel framework [Pagonabarraga, I.; Frenkel, D.

Coarse-grained polarizable soft solvent models, with applications in dissipative particle dynamics.

We critically examine a broad class of explicitly polarizable soft solvent models aimed at applications in dissipative particle dynamics. We obtain the dielectric permittivity using the fluctuating box dipole method in linear response theory and verify the models in relation to several test cases, including demonstrating ion desorption from an oil-water interface due to image charge effects. We additionally compute the Kirkwood factor and find that it uniformly lies in the range gK≃0.

The Management of Dysfunctional Gallbladder Disease and the Role of Laparoscopic Cholecystectomy on Symptom Improvement: A Retrospective Cohort Study.

Background Biliary dyskinesia (BD) is a disorder characterised by abdominal pain of biliary origin (i.e., sudden steady pain at the right upper quadrant of the abdomen or the epigastrium, the absence of gallstones on ultrasound (US)), and a decreased gallbladder ejection fraction (GBEF) on a cholecystokinin-cholescintigraphy hepatobiliary iminodiacetic acid (CCK-HIDA) scan.

Local density dependent potentials for an underlying van der Waals equation of state: A simulation and density functional theory analysis.

There is an ever increasing use of local density dependent potentials in the mesoscale modeling of complex fluids. Questions remain, though, about the dependence of the thermodynamic and structural properties of such systems on the cutoff distance used to calculate these local densities. These questions are particularly acute when it comes to the stability and structure of the vapor/liquid interface.

Microstructural and thermodynamic characterization of wormlike micelles formed by polydisperse ionic surfactant solutions.

For industrial applications of self-assembled wormlike micelles, measurement and characterization of a micellar material's microstructure and rheology are paramount for the development and deployment of new high-performing and cost-effective formulations. Within this workflow, there are significant bottlenecks associated with experimental delays and a lack of transferability of results from one chemistry to another. In this work, we outline a process to predict microscopic and thermodynamic characteristics of wormlike micelles directly from rheological data by combining a more robust and efficient fitting algorithm with a recently published constitutive model called the Toy Shuffling model [J.

Hierarchical Aggregation in a Complex Fluid─The Role of Isomeric Interconversion.

There is an ever-increasing body of evidence that metallic complexes involving amphiliphic ligands do not form normal solutions in organic solvents. Instead, they form complex fluids with intricate structures. For example, the metallic complexes may aggregate into clusters, and these clusters themselves may aggregate into superclusters.

Molecular Dynamics Study of the Aggregation Behavior of ,,','-Tetraoctyl Diglycolamide.

Liquid-liquid extraction is a commonly used technique to separate metals and is a process that has particular relevance to the nuclear industry. There has been a drive to use environmentally friendly ligands composed only of carbon, hydrogen, nitrogen, and oxygen. One example is the i-SANEX process that has been developed to separate minor actinides from spent nuclear fuel.

A Telescoping View of Solute Architectures in a Complex Fluid System.

Short- and long-range correlations between solutes in solvents can influence the macroscopic chemistry and physical properties of solutions in ways that are not fully understood. The class of liquids known as complex (structured) fluids-containing multiscale aggregates resulting from weak self-assembly-are especially important in energy-relevant systems employed for a variety of chemical- and biological-based purification, separation, and catalytic processes. In these, solute (mass) transfer across liquid-liquid (water, oil) phase boundaries is the core function.

A Novel Microemulsion Phase Transition: Toward the Elucidation of Third-Phase Formation in Spent Nuclear Fuel Reprocessing.

We present evidence that the transition between organic and third phases, which can be observed in the plutonium uranium reduction extraction (PUREX) process at high metal loading, is an unusual transition between two isotropic bicontinuous microemulsion phases. As this system contains so many components, however, we have been seeking first to investigate the properties of a simpler system, namely, the related metal-free, quaternary water/n-dodecane/nitric acid/tributyl phosphate (TBP) system. This quaternary system has been shown to exhibit, under appropriate conditions, three coexisting phases: a light organic phase, an aqueous phase, and the so-called third phase.

Macroscopic chiral symmetry breaking in monolayers of achiral nonconvex platelets.

The fabrication of chiral structures using achiral building blocks is a fundamental problem that remains a challenge in materials science. In this work we present a molecular dynamics simulation study of nonconvex polygonal platelets, interacting via soft-repulsive interactions, that are confined in two-dimensional space. These particle models are designed to promote, even at moderate densities, a natural offset displacement between the edges of neighbouring particles.

Phase behaviour of hard board-like particles.

We examine the phase behaviour of colloidal suspensions of hard board-like particles (HBPs) as a function of their shape anisotropy, and observe a fascinating spectrum of nematic, smectic, and columnar liquid-crystalline phases, whose formation is entirely driven by excluded volume effects. We map out the phase diagram of short and long HBPs by gradually modifying their shape from prolate to oblate and investigate the long-range order of the resulting morphologies along the phase directors and perpendicularly to them. The intrinsic biaxial nature of these particles promotes the formation of translationally ordered biaxial phases, but does not show solid evidence that it would, per se, promote the formation of the biaxial nematic phase.

Rare case of gallbladder agenesis presenting with pancreatitis.

Gallbladder agenesis (GA) is a rare congenital abnormality with an incidence of 0.01-0.09%.

Comparative Molecular Dynamics Study on Tri-n-butyl Phosphate in Organic and Aqueous Environments and Its Relevance to Nuclear Extraction Processes.

A refined model for tri-n-butyl phosphate (TBP), which uses a new set of partial charges generated from our ab initio density functional theory calculations, has been proposed in this study. Molecular dynamics simulations are conducted to determine the thermodynamic properties, transport properties, and the microscopic structures of liquid TBP, TBP/water mixtures, and TBP/n-alkane mixtures. These results are compared with those obtained from four other TBP models, previously described in the literature.

Note: A dual temperature closed loop batch reactor for determining the partitioning of trace gases within CO2-water systems.

An experimental approach is presented which can be used to determine partitioning of trace gases within CO2-water systems. The key advantages of this system are (1) The system can be isolated with no external exchange, making it ideal for experiments with conservative tracers. (2) Both phases can be sampled concurrently to give an accurate composition at each phase at any given time.

Optimizing Noble Gas-Water Interactions via Monte Carlo Simulations.

In this work we present optimized noble gas-water Lennard-Jones 6-12 pair potentials for each noble gas. Given the significantly different atomic nature of water and the noble gases, the standard Lorentz-Berthelot mixing rules produce inaccurate unlike molecular interactions between these two species. Consequently, we find simulated Henry's coefficients deviate significantly from their experimental counterparts for the investigated thermodynamic range (293-353 K at 1 and 10 atm), due to a poor unlike potential well term (εij).

Thermodynamics of the self-assembly of non-ionic chromonic molecules using atomistic simulations. The case of TP6EO2M in aqueous solution.

Atomistic molecular dynamic simulations have been performed for the non-ionic chromonic liquid crystal 2,3,6,7,10,11-hexa-(1,4,7-trioxa-octyl)-triphenylene (TP6EO2M) in aqueous solution. TP6EO2M molecules consist of a central poly-aromatic core (a triphenylene ring) functionalized by six hydrophilic ethyleneoxy (EO) chains, and have a strong tendency to aggregate face-to-face into stacks even in very dilute solution. We have studied self-assembly of the molecules in the low concentration range corresponding to an isotropic solution of aggregates, using two force fields GAFF and OPLS.

Self-assembly and mesophase formation in a non-ionic chromonic liquid crystal system: insights from dissipative particle dynamics simulations.

Results are presented from a dissipative particle dynamics (DPD) simulation of a model non-ionic chromonic system, TP6EO2M, composed of a poly(ethylene glycol) functionalised aromatic (triphenylene) core. The simulations demonstrate self-assembly of chromonic molecules to form single molecule stacks in solution at low concentrations, the formation of a nematic mesophase at higher concentrations and a columnar phase in the more concentrated regime. The simulation model used allows very large system sizes, of many thousands of particles, to be studied.

Obturator hernia - MRI image.

Obturator hernia although considered a rare entity is the most frequently encountered pelvic floor hernia. Since the first published report in the 18th century, their unusual and unfamiliar clinical presentation still represents a diagnostic dilemma for the modern day clinician. A detailed history and clinical examination in our thin, elderly female patient who presented with intermittent small bowel obstruction and symptoms of right obturator nerve compression with a positive Howship-Romberg sign was crucial in establishing a diagnosis.

Platelet counting with the BD Accuri(TM) C6 flow cytometer.

The Accuri™ C6 is a compact flow cytometer that uses a peristaltic pump with a laminar flow fluidic system and can measure absolute cell counts. In this study we have evaluated this method with the International Reference Method (IRM) simultaneously measured on both the Accuri™ C6 and a reference flow cytometer. After optimisation of sample labelling conditions, final dilutions and flow cytometer settings, a comparison of the absolute fluorescent platelet count with the RBC/platelet ratio on the C6 and the IRM was then performed in 144 patient samples with a full range of platelet counts (range 2-650 × 10(9)/l).

Screening properties of Gaussian electrolyte models, with application to dissipative particle dynamics.

We investigate the screening properties of Gaussian charge models of electrolyte solutions by analysing the asymptotic behaviour of the pair correlation functions. We use a combination of Monte Carlo simulations with the hyper-netted chain integral equation closure, and the random phase approximation, to establish the conditions under which a screening length is well defined and the extent to which it matches the expected Debye length. For practical applications, for example, in dissipative particle dynamics, we are able to summarise our results in succinct rules-of-thumb which can be used for mesoscale modeling of electrolyte solutions.

Phase behaviour and the random phase approximation for ultrasoft restricted primitive models.

Phase separation of the ultrasoft restricted primitive model (URPM) with gaussian charges is re-investigated in the random phase approximation (RPA)--the "Level A" approximation discussed by Nikoubashman, Hansen, and Kahl [J. Chem. Phys.

An improved high performance liquid chromatography-fluorescence detection method for the analysis of major phenolic compounds in cigarette smoke and smokeless tobacco products.

An improved HPLC method has been developed for the determination of major phenolic compounds in cigarette smoke. A novel reversed phase column with a pentafluorophenylpropyl (PFP) ligand in the stationary phase was chosen to separate the positional isomers (p-, m-, and o-cresols). Methanol instead of acetonitrile was used as the organic mobile phase component to improve the separation of the isomers and cope with the crisis of global acetonitrile shortage in 2009.

High-level virial theory of hard spheroids.

We present a method for calculating high-order virial expansions of the isotropic-nematic phase transition which we apply here to hard spheroids. Studying a range of aspect ratios, for both oblate and prolate particles, we obtain equations of state, coexistence densities, and nematic order parameters, using expansions truncated at up to eighth virial level. For particles of large aspect ratios our results show rapid convergence, with truncation at sixth order sufficient to give excellent agreement with simulation data.

Thermodynamic stability of the cubatic phase of hard cut spheres evaluated by expanded ensemble simulations.

The system of hard cut spheres (disk-shaped particles formed by symmetrically truncating the end caps of a sphere) exhibits an intriguing "cubatic" phase with cubic orientational symmetry. However, it is unclear whether this phase is metastable with respect to the columnar phase. We attempt to provide an answer to this question by carrying out free energy calculations by the expanded ensemble Monte Carlo method.

Theory and computer simulation for the cubatic phase of cut spheres.

The phase behavior of a system of hard-cut spheres has been studied using a high-order virial theory and by Monte Carlo simulation. The cut-sphere particles are disks of thickness L formed by symmetrically truncating the end caps of a sphere of diameter D . The virial theory predicts a stable nematic phase for aspect ratio LD=0.