@article {2418, title = {Vapour-liquid phase transition of dipolar particles}, journal = {Molecular Physics}, volume = {107}, number = {4-6}, year = {2009}, note = {ISI Document Delivery No.: 448EATimes Cited: 5Cited Reference Count: 54Ganzenmueller, Georg Patey, G. N. Camp, Philip J.}, pages = {403-413}, type = {Article}, abstract = {The question of whether a vapour-liquid phase transition exists in systems of particles with purely dipolar interactions is examined. New Monte Carlo simulation results are presented for the dipolar Yukawa hard sphere (DYHS) fluid with very small values of the attractive Yukawa well depth, almost two orders of magnitude smaller than the characteristic dipolar interaction energy. In this way, it is possible to approach the dipolar hard sphere (DHS) limit. It is found that phase separation is not observable beyond a critical value of the Yukawa energy parameter, even though in thermodynamic and structural terms, the DYHS and DHS systems are very similar. It is suggested that either some very subtle physics distinguishes the DYHS and DHS systems, or the observation of a phase transition in DHSs is precluded by finite-size effects.}, keywords = {BEHAVIOR, COEXISTENCE, dipolar hard spheres, FERROFLUIDS, FLUIDS, HARD-SPHERES, Monte Carlo simulation, MONTE-CARLO, ORDER, SIMULATION, SYSTEM, THERMODYNAMICS, vapour-liquid transition}, isbn = {0026-8976}, url = {://000266244700014}, author = {Ganzenmuller, G. and Patey, G. N. and Camp, P. J.} } @article {1412, title = {Nanoscopic liquid bridges between chemically patterned atomistic walls}, journal = {Journal of Physical Chemistry B}, volume = {110}, number = {8}, year = {2006}, note = {ISI Document Delivery No.: 020WQTimes Cited: 6Cited Reference Count: 38}, month = {Mar}, pages = {3764-3772}, type = {Article}, abstract = {A binary liquid mixture, containing the Lennard-Jones molecules A and B, in equilibrium with a bulk liquid reservoir near the point of phase separation, confined between atomistic chemically patterned walls, is studied by grand canonical Monte Carlo simulations. In the bulk, the B-rich phase is stable and the A-rich phase is metastable. The walls bear patches attractive to A; when the walls are close, A-rich liquid bridges condense between the patches. The normal and lateral forces on the walls are measured as a function of the wall separation and of the lateral displacement between the patches on opposite walls. When there are one or two molecular layers in the bridge and the wall lattice constant is close to that of crystalline A, the normal and lateral forces depend strongly on the registry of the wall lattices, varying in an oscillatory manner.}, keywords = {BEHAVIOR, capillary, CONDENSATION, FILMS, FLUIDS, FORCES, INDUCED PHASE-TRANSITIONS, MOLECULARLY THIN-LAYERS, PORES, SHEAR, STRUCTURED WALLS}, isbn = {1520-6106}, url = {://000235944300039}, author = {Hemming, C. J. and Patey, G. N.} } @article {1259, title = {Colloid-induced structure in liquid crystal media}, journal = {Journal of Chemical Physics}, volume = {122}, number = {12}, year = {2005}, note = {ISI Document Delivery No.: 915HDTimes Cited: 7Cited Reference Count: 26}, month = {Mar}, pages = {8}, type = {Article}, abstract = {The structural perturbations induced by colloidal particles immersed in a model nematic subjected to an external field are calculated employing integral equation methods. Maps of the density-orientational distribution about a colloidal particle are obtained, and these provide a microscopic picture of the colloid{\textquoteright}s nematic coat. We focus on colloidal particles that favor homeotropic anchoring, but planar anchoring cases are also considered. The range and structure of the nematic coat is shown to be significantly influenced by the nature of the anchoring, the size of the colloidal particle, the range and strength of the colloid-nematogen interaction, and the external field strength. All of these factors are discussed.}, keywords = {FIELD, FLUIDS, INTEGRAL-EQUATION THEORY, PHASE, SIMULATION, SPHERICAL-PARTICLE, TOPOLOGICAL DEFECTS}, isbn = {0021-9606}, url = {://000228287900062}, author = {Sokolovska, T. G. and Sokolovskii, R. O. and Patey, G. N.} } @article {626, title = {Optimization of cellular nucleotide extraction and sample preparation for nucleotide pool analyses using capillary electrophoresis}, journal = {Journal of Chromatography B-Analytical Technologies in the Biomedical and Life Sciences}, volume = {788}, number = {1}, year = {2003}, note = {ISI Document Delivery No.: 664KCTimes Cited: 12Cited Reference Count: 28}, month = {May}, pages = {103-111}, type = {Article}, abstract = {Cell extraction and further sample preparation for nucleotide pool analysis using capillary electrophoresis was faster and simpler using volatile extraction solvents (e.g. organic solvents and de-ionized water) compared to the commonly applied acids dissolved in water (e.g. perchloric acid and trichloracetic acid). Temperature had to be controlled during the whole sample preparation process to prevent degradation, and extracts had to be cleaned from proteins and other large molecules prior to capillary electrophoretic analysis to improve reproducibility. Capillary electrophoresis using borate and cyclodextrins in the background electrolyte was used for determining 11 cellular nucleotides simultaneously. In order to optimize the assay, 0-100\% acetonitrile, 0-100\% ethanol, and 0-100\% methanol in de-ionized water were applied to extract nucleotides from mouse lymphoma cells, and nucleotide yields, recovery, and reproducibility were compared. The assay met the commonly accepted validation limits for biological fluids, if 20-80\% acetonitrile in water and 40-60\% ethanol in water were used as extraction solvents. (C) 2003 Elsevier Science B.V. All rights reserved.}, keywords = {CELLS, dynamic pH junction, FLUIDS, MIGRATION BEHAVIOR, NUCLEOSIDES, nucleotides, PERFORMANCE LIQUID-CHROMATOGRAPHY, QUANTITATIVE-ANALYSIS, SEPARATION, TISSUES, TRIPHOSPHATES}, isbn = {1570-0232}, url = {://000182059400012}, author = {Grob, M. K. and O{\textquoteright}Brien, K. and Chu, J. J. and Chen, D. D. Y.} } @article {453, title = {Dielectric relaxation of chained ferrofluids}, journal = {Journal of Chemical Physics}, volume = {116}, number = {15}, year = {2002}, note = {ISI Document Delivery No.: 537PGTimes Cited: 13Cited Reference Count: 18}, month = {Apr}, pages = {6731-6737}, type = {Article}, abstract = {Molecular and Brownian dynamics simulations are used to investigate the frequency-dependent dielectric relaxation of ferrofluids, with the objective of identifying features characteristic of dipolar chain formation at low densities. It is shown that the presence of chains gives rise to a high frequency band associated with the vibrational motion of dipoles within the chains. This band serves as a "signature" of association and is not present in dipolar fluids at higher, liquid-like densities. A simple theory that traps the basic features of the relaxation behavior is also presented. (C) 2002 American Institute of Physics.}, keywords = {FLUIDS, PHASE, SCATTERING, SIMULATION, SPHERES}, isbn = {0021-9606}, url = {://000174767200039}, author = {Murashov, V. V. and Camp, P. J. and Patey, G. N.} } @article {445, title = {Molecular dynamics simulations of a ferroelectric nematic liquid under shear flow}, journal = {Journal of Chemical Physics}, volume = {117}, number = {18}, year = {2002}, note = {ISI Document Delivery No.: 610YYTimes Cited: 5Cited Reference Count: 47}, month = {Nov}, pages = {8551-8564}, type = {Article}, abstract = {We perform nonequilibrium molecular dynamics simulations to examine the change in orientational order of a ferroelectric nematic liquid crystal under shear flow, specifically planar Couette flow. The orientational order is found to decrease with increasing shear rate. This drop in orientational order is not due to structural changes but is rather a result of the director dynamics being flow unstable. Employing both nonequilibrium and equilibrium molecular dynamics with the director orientation fixed, we determine the shear and twist viscosities which relate the pressure tensor to the shear or strain rate tensor in a nematic liquid crystal under flow. The Miesowicz viscosities are then obtained from linear combinations of the shear and twist viscosities. The short-range spatial structure of the ferroelectric nematic liquid crystal is similar to that of a ferroelectric tetragonal I lattice. The relative magnitudes of the Miesowicz viscosities can be understood by examining the shear stress response of this lattice to a shear deformation. (C) 2002 American Institute of Physics.}, keywords = {BOUNDARY-CONDITIONS, COMPUTER-SIMULATION, CRYSTALS, FLUIDS, MONTE-CARLO, PHASE-TRANSITIONS, rheology, STATE, VISCOSITY}, isbn = {0021-9606}, url = {://000178990700045}, author = {McWhirter, J. L. and Patey, G. N.} } @article {4848, title = {Crystallization of dipolar spheres: A discussion of second-order density functional theory}, journal = {Journal of Chemical Physics}, volume = {112}, number = {24}, year = {2000}, note = {ISI Document Delivery No.: 324HYTimes Cited: 6Cited Reference Count: 43}, month = {Jun}, pages = {10949-10956}, type = {Article}, abstract = {We investigate the application of second-order density functional theory to the crystallization of dipolar hard and soft spheres. It is shown that the results are highly sensitive to the repulsive part of the pair potential, and to the symmetry of the fluid phase considered in the density functional theory. In general, the theoretical results for dipolar soft spheres (with r(-12) repulsion) are found to be physically more reasonable than those obtained for dipolar hard spheres. In particular, the fluid-solid density gap is greatly reduced and lies in the range expected on physical grounds and from simulations. However, theories constructed by expanding about the isotropic fluid phase overestimate the stability of the ferroelectric solid for both models, and fail to predict the stable ferroelectric fluids found in computer simulations. We have carried out calculations using ferroelectric dipolar fluids with both perfect and fluctuating orientational order as "starting points" in the density functional expansion. The results demonstrate the high sensitivity of the theory to the underlying fluid state, and strongly indicate the existence of stable ferroelectric fluids in accord with computer simulations. (C) 2000 American Institute of Physics. [S0021-9606(00)50924-6].}, keywords = {FLUIDS, HARD-SPHERES, INTEGRAL-EQUATIONS, LIQUID-VAPOR INTERFACE, NEMATIC PHASE, orientational order, PHASE-TRANSITIONS, SOFT SPHERES, SOLID-PHASES, STABILITY}, isbn = {0021-9606}, url = {://000087617300033}, author = {Klapp, S. H. L. and Patey, G. N.} } @article {4748, title = {Structure and scattering in colloidal ferrofluids}, journal = {Physical Review E}, volume = {62}, number = {4}, year = {2000}, note = {ISI Document Delivery No.: 365YATimes Cited: 67Cited Reference Count: 32Part B}, month = {Oct}, pages = {5403-5408}, type = {Article}, abstract = {The structure of a model colloidal ferrofluid, the dipolar hard-sphere fluid, at low temperature has been investigated using Monte Carlo simulations. Extensive particle association into chainlike and ringlike clusters is observed at low density. The structure factors have been calculated, and are analyzed with the aid of simple scaling arguments. We describe the progression of fluid structures from the low-density associated phase, to the high-density liquid phase. This paper may he of help in obtaining an experimental observation of a fluid-fluid transition in colloidal ferrofluids.}, keywords = {DIPOLAR HARD-SPHERES, FLUIDS, LIQUID, LIVING, LOW-DENSITIES, MODEL POLAR CLUSTERS, MONTE-CARLO, orientational order, PHASES, POLYMERS, SYSTEMS}, isbn = {1063-651X}, url = {://000089977000025}, author = {Camp, P. J. and Patey, G. N.} } @article {4497, title = {Ion association and condensation in primitive models of electrolyte solutions}, journal = {Journal of Chemical Physics}, volume = {111}, number = {19}, year = {1999}, note = {ISI Document Delivery No.: 251GQTimes Cited: 34Cited Reference Count: 32}, month = {Nov}, pages = {9000-9008}, type = {Article}, abstract = {{Monte Carlo simulations have been used to investigate condensation and ion association in primitive models of electrolyte solutions. We have examined models in which the ions have equal diameter, the cation charge is +Zq, and the anion charge is -q, with Z=1}, keywords = {BINARY MIXTURE, CHARGED HARD-SPHERE, COEXISTENCE, CONSOLUTE POINT, CRITICAL EXPONENT, CROSSOVER, FLUIDS, FREE-ENERGY, MONTE-CARLO, PHASE-EQUILIBRIA}, isbn = {0021-9606}, url = {://000083437400030}, author = {Camp, P. J. and Patey, G. N.} } @article {4662, title = {Phase behavior of ionic solutions: Comparison of the primitive and explicit solvent models}, journal = {Journal of Chemical Physics}, volume = {110}, number = {3}, year = {1999}, note = {ISI Document Delivery No.: 156YMTimes Cited: 20Cited Reference Count: 39}, month = {Jan}, pages = {1633-1637}, type = {Article}, abstract = {Grand canonical Monte Carlo calculations are used to investigate the demixing transition in model ionic solutions where the solvent is explicitly included. Charged hard sphere ions in hard sphere, dipolar hard sphere and quadrupolar hard sphere solvents are considered and the results are compared with the primitive (continuum solvent) model. For all solvents considered, it is found that the demixing transition is in the same general region of the phase diagram and is roughly described by liquid-vapor equilibrium in the primitive model. However, details such as the precise location of the critical point and the width of the unstable region depend upon the exact nature of the solvent. (C) 1999 American Institute of Physics. [S0021-9606(99)50203-1].}, keywords = {BINARY, CHARGED HARD-SPHERES, CONSOLUTE POINT, CRITICAL EXPONENT, ELECTROLYTE-SOLUTIONS, EQUILIBRIA, FLUIDS, FREE-ENERGY, LIQUID-VAPOR COEXISTENCE, MIXTURE, MONTE-CARLO}, isbn = {0021-9606}, url = {://000078030500034}, author = {Shelley, J. C. and Patey, G. N.} } @article {4218, title = {Prediction from molecular shape of solute orientational order in liquid crystals}, journal = {Chemical Reviews}, volume = {98}, number = {6}, year = {1998}, note = {ISI Document Delivery No.: 127TNTimes Cited: 82Cited Reference Count: 154}, month = {Sep-Oct}, pages = {2359-2387}, type = {Review}, keywords = {ATOM-ATOM POTENTIALS, COUPLINGS, ELECTRIC-FIELD GRADIENT, FLUIDS, HARD-PARTICLE, ISOMERIC STATE APPROXIMATION, MONTE-CARLO SIMULATIONS, MULTIPLE-QUANTUM H-1-NMR, NEMATIC SOLVENTS, NUCLEAR MAGNETIC-RESONANCE, PARTIALLY ORIENTED MOLECULES, SPIN DIPOLAR}, isbn = {0009-2665}, url = {://000076366800007}, author = {Burnell, E. E. and de Lange, C. A.} } @article {3786, title = {Remarks on the forces between macroscopic particles in solution}, journal = {Berichte Der Bunsen-Gesellschaft-Physical Chemistry Chemical Physics}, volume = {100}, number = {6}, year = {1996}, note = {ISI Document Delivery No.: UW575Times Cited: 21Cited Reference Count: 221st International Symposium on Polyelectrolytes/Discussion Meeting of Deutsche-Bunsen-Gesellschaft-fur-Physikalische-Chemie on Polyelectrolytes in Solution and at InterfacesSEP 18-22, 1995POTSDAM, GERMANYDeut Bunsen Gesell Phys chem}, month = {Jun}, pages = {885-888}, type = {Proceedings Paper}, abstract = {Some interesting aspects of the forces acting between macroscopic objects (spheres and plates) immersed in solution are discussed. These include attractive forces between like-charged objects in primitive model electrolyte solutions, van der Waals forces in molecular solvents, and strong attractive interactions related to cavitation or separation-induced evaporation of liquids between inert or {\textquoteright}{\textquoteright}solvophobic{\textquoteright}{\textquoteright} walls.}, keywords = {ATTRACTION, COLLOIDAL PARTICLES, ELECTRICAL DOUBLE-LAYER, ELECTROLYTE SOLUTION, FLUIDS, HYDROPHOBIC SURFACES, HYPERNETTED-CHAIN APPROXIMATION, LENNARD-JONES, molecular interactions, MONTE-CARLO, solutions, SYMMETRICAL POISSON-BOLTZMANN}, isbn = {0005-9021}, url = {://A1996UW57500032}, author = {Patey, G. N.} } @article {2929, title = {DYNAMIC PROPERTIES OF A FERROELECTRIC NEMATIC LIQUID-CRYSTAL}, journal = {Physical Review E}, volume = {47}, number = {4}, year = {1993}, note = {ISI Document Delivery No.: KZ507Times Cited: 10Cited Reference Count: 18}, month = {Apr}, pages = {2954-2957}, type = {Note}, abstract = {Molecular-dynamics simulations are used to investigate the dynamical properties of a ferroelectric nematic liquid crystal. The results are also relevant to electrorheological fluids and to ferrofluids. Translational and rotational diffusion constants parallel and perpendicular to the director are reported and discussed. Dipole-dipole reorientational correlation functions are calculated and compared with theoretical models.}, keywords = {ANISOTROPY, ELECTROSTATIC SYSTEMS, FLUIDS, MOLECULAR-DYNAMICS, PERIODIC BOUNDARY-CONDITIONS, SIMULATION, VISCOSITY}, isbn = {1063-651X}, url = {://A1993KZ50700094}, author = {Wei, D. Q. and Patey, G. N.} } @article {7146, title = {DIELECTRIC-RELAXATION OF ELECTROLYTE-SOLUTIONS}, journal = {Journal of Chemical Physics}, volume = {94}, number = {10}, year = {1991}, note = {ISI Document Delivery No.: FL001Times Cited: 29Cited Reference Count: 49}, month = {May}, pages = {6795-6806}, type = {Article}, abstract = {The dielectric relaxation theory of electrolyte solutions is formulated in terms of solvent-solvent, ion-ion, and ion-solvent van Hove time correlation functions. General wave vector frequency-dependent expressions are given for the longitudinal components of the relevant (i.e., polarization-polarization, current-current, current-polarization, polarization-current) time correlation functions and of the susceptibility, dielectric, and conductivity tensors. The Kerr theory relating the distinct and self parts of the van Hove functions is extended to mixtures of molecular fluids and solved explicitly in the k {\textendash}> 0 limit for solutions of spherical ions (assuming that the self part of the van Hove functions is given by Fick{\textquoteright}s law) immersed in polar solvents. At this level of theory, the van Hove functions, the time correlation functions and the susceptibilities are all found to depend upon coupled ion-solvent motion. However, the dynamical coupling terms are shown to cancel exactly in the final expressions for the conductivity and dielectric constant yielding relatively simple results. Specifically, the conductivity obtained is independent of frequency and is related to the self diffusion constants of the ions by the Nernst-Einstein expression. If a spherical diffusor model is chosen for the solvent, then the frequency-dependent dielectric constant is given by a Debye-type formula with a concentration dependent relationship connecting the Debye and self reorientational relaxation times of the solvent. These results are discussed in the context of previous theories and experimental observations. It is shown that, although obviously oversimplified, the present theory does qualitatively predict the correct concentration dependence of the observed relaxation times for a number of salt solutions.}, keywords = {DIPOLAR LIQUIDS, DISPERSION, FLUIDS, friction, INVARIANT EXPANSION, LIQUIDS, MEAN SPHERICAL MODEL, MOLECULAR THEORY, ORNSTEIN-ZERNIKE EQUATION, POLAR, TRANSLATIONAL DIFFUSION}, isbn = {0021-9606}, url = {://A1991FL00100048}, author = {Wei, D. Q. and Patey, G. N.} }