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Julia M. Yeomans

Bio: Julia M. Yeomans is an academic researcher from University of Oxford. The author has contributed to research in topics: Lattice Boltzmann methods & Liquid crystal. The author has an hindex of 69, co-authored 410 publications receiving 18437 citations. Previous affiliations of Julia M. Yeomans include Eindhoven University of Technology & Sultan Qaboos University.


Papers
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TL;DR: The details of a lattice Boltzmann approach to phase separation in nonideal one- and two-component fluids are presented and the kinetics of the approach to equilibrium lie within the expected universality classes.
Abstract: We present the details of a lattice Boltzmann approach to phase separation in nonideal one- and two-component fluids. The collision rules are chosen such that the equilibrium state corresponds to an input free energy and the bulk flow is governed by the continuity, Navier-Stokes, and, for the binary fluid, a convection-diffusion equation. Numerical results are compared to simple analytic predictions to confirm that the equilibrium state is indeed thermodynamically consistent and that the kinetics of the approach to equilibrium lie within the expected universality classes. The approach is compared to other lattice Boltzmann simulations of nonideal systems. \textcopyright{} 1996 The American Physical Society.

1,170 citations

Journal ArticleDOI
TL;DR: A lattice Boltzmann scheme able to model the hydrodynamics of phase separation and two-phase flow is described and Thermodynamic consistency is ensured by introducing a non-ideal pressure tensor directly into the collision operator.
Abstract: A lattice Boltzmann scheme able to model the hydrodynamics of phase separation and two-phase flow is described. Thermodynamic consistency is ensured by introducing a nonideal pressure tensor directly into the collision operator. We also show how an external chemical potential can be used to supplement standard boundary conditions in order to investigate the effect of wetting on phase separation and fluid flow in confined geometries. The approach has the additional advantage of reducing many of the unphysical discetrization problems common to previous lattice Boltzmann methods.

1,116 citations

Journal ArticleDOI
TL;DR: In this paper, the authors combine experiments, particle simulations, and continuum theory to identify the statistical properties of self-sustained meso-scale turbulence in active systems, and propose a minimal continuum model for incompressible bacterial flow.
Abstract: Turbulence is ubiquitous, from oceanic currents to small-scale biological and quantum systems. Self-sustained turbulent motion in microbial suspensions presents an intriguing example of collective dynamical behavior among the simplest forms of life and is important for fluid mixing and molecular transport on the microscale. The mathematical characterization of turbulence phenomena in active nonequilibrium fluids proves even more difficult than for conventional liquids or gases. It is not known which features of turbulent phases in living matter are universal or system-specific or which generalizations of the Navier–Stokes equations are able to describe them adequately. Here, we combine experiments, particle simulations, and continuum theory to identify the statistical properties of self-sustained meso-scale turbulence in active systems. To study how dimensionality and boundary conditions affect collective bacterial dynamics, we measured energy spectra and structure functions in dense Bacillus subtilis suspensions in quasi-2D and 3D geometries. Our experimental results for the bacterial flow statistics agree well with predictions from a minimal model for self-propelled rods, suggesting that at high concentrations the collective motion of the bacteria is dominated by short-range interactions. To provide a basis for future theoretical studies, we propose a minimal continuum model for incompressible bacterial flow. A detailed numerical analysis of the 2D case shows that this theory can reproduce many of the experimentally observed features of self-sustained active turbulence.

803 citations

Book
01 Jan 1992
TL;DR: In this article, the renormalization group is used for the transfer matrix series expansion in the model of mean field theory and thermodynamics, and for the series expansions in Monte Carlo simulations.
Abstract: Introduction Statistical mechanics and thermodynamics Models Mean-field theories The transfer matrix Series expansions Monte Carlo simulations The renormalization group Implementations of the renormalization group.

788 citations

Journal ArticleDOI
TL;DR: By designing surfaces with tapered micro/nanotextures which behave as harmonic springs, the timescales become independent of the impact velocity, allowing the occurrence of pancake bouncing and rapid drop detachment over a wide range of impact velocities.
Abstract: When a water drop bounces back from a hydrophobic surface, its initial, spherical shape is usually restored. Now, experiments with a specially engineered superhydrophobic surface made from micrometre-sized tapered pillars covered with copper oxide ‘nanoflowers’ show that droplets can bounce back with a flat, pancake-like shape. Engineering surfaces that promote rapid drop detachment1,2 is of importance to a wide range of applications including anti-icing3,4,5, dropwise condensation6 and self-cleaning7,8,9. Here we show how superhydrophobic surfaces patterned with lattices of submillimetre-scale posts decorated with nanotextures can generate a counter-intuitive bouncing regime: drops spread on impact and then leave the surface in a flattened, pancake shape without retracting. This allows a fourfold reduction in contact time compared with conventional complete rebound 1,10,11,12,13. We demonstrate that the pancake bouncing results from the rectification of capillary energy stored in the penetrated liquid into upward motion adequate to lift the drop. Moreover, the timescales for lateral drop spreading over the surface and for vertical motion must be comparable. In particular, by designing surfaces with tapered micro/nanotextures that behave as harmonic springs, the timescales become independent of the impact velocity, allowing the occurrence of pancake bouncing and rapid drop detachment over a wide range of impact velocities.

698 citations


Cited by
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[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

28 Jul 2005
TL;DR: PfPMP1)与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1(PfPMP1)与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员,通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

18,940 citations

Journal ArticleDOI
TL;DR: An overview of the lattice Boltzmann method, a parallel and efficient algorithm for simulating single-phase and multiphase fluid flows and for incorporating additional physical complexities, is presented.
Abstract: We present an overview of the lattice Boltzmann method (LBM), a parallel and efficient algorithm for simulating single-phase and multiphase fluid flows and for incorporating additional physical complexities. The LBM is especially useful for modeling complicated boundary conditions and multiphase interfaces. Recent extensions of this method are described, including simulations of fluid turbulence, suspension flows, and reaction diffusion systems.

6,565 citations

Journal ArticleDOI
TL;DR: In this article, a review of dissipative particle dynamics (DPD) as a mesoscopic simulation method is presented, and a link between these parameters and χ-parameters in Flory-Huggins-type models is made.
Abstract: We critically review dissipative particle dynamics (DPD) as a mesoscopic simulation method. We have established useful parameter ranges for simulations, and have made a link between these parameters and χ-parameters in Flory-Huggins-type models. This is possible because the equation of state of the DPD fluid is essentially quadratic in density. This link opens the way to do large scale simulations, effectively describing millions of atoms, by firstly performing simulations of molecular fragments retaining all atomistic details to derive χ-parameters, then secondly using these results as input to a DPD simulation to study the formation of micelles, networks, mesophases and so forth. As an example application, we have calculated the interfacial tension σ between homopolymer melts as a function of χ and N and have found a universal scaling collapse when σ/ρkBTχ0.4 is plotted against χN for N>1. We also discuss the use of DPD to simulate the dynamics of mesoscopic systems, and indicate a possible problem with...

3,837 citations