427 research outputs found
Constant-angle surfaces in liquid crystals
We discuss some properties of surfaces in R3 whose unit normal has constant angle with an assigned direction field. The constant angle condition can be rewritten as an Hamilton-Jacobi equation correlating the surface and the direction field. We focus on examples motivated by the physics of interfaces in liquid crystals and of layered fluids, and discuss the properties of the constant-angle surfaces when the direction field is singular along a line (disclination) or at a point (hedgehog defect
Macroporous materials: microfluidic fabrication, functionalization and applications
This article provides an up-to-date highly comprehensive overview (594 references) on the state of the art of the synthesis and design of macroporous materials using microfluidics and their applications in different fields
Parity Breaking in Nematic Tactoids
We theoretically investigate under what conditions the director field in a
spindle-shaped nematic droplet or tactoid obtains a twisted, parity-broken
structure. By minimizing the sum of the bulk elastic and surface energies, we
show that a twisted director field is stable if the twist and bend elastic
constants are small enough compared to the splay elastic constant, but only if
the droplet volume is larger than some minimum value. We furthermore show that
the transition from an untwisted to a twisted director-field structure is a
sharp function of the various control parameters. We predict that suspensions
of rigid, rod-like particles cannot support droplets with a parity broken
structure, whereas they could possibly occur in those of semi-flexible,
worm-like particles.Comment: 20 pages, 9 figures, submitted to Journal of Physics: Condensed
Matte
Fluid-crystal coexistence for proteins and inorganic nanocolloids: dependence on ionic strength
We investigate theoretically the fluid-crystal coexistence of solutions of
globular charged nanoparticles like proteins and inorganic colloids. The
thermodynamic properties of the fluid phase are computed via the optimized
Baxter model. This is done specifically for lysozyme and silicotungstates for
which the bare adhesion parameters are evaluated via the experimental second
virial coefficients. The electrostatic free energy of the crystal is
approximated by supposing the cavities in the interstitial phase between the
particles are spherical in form. In the salt-free case a Poisson-Boltzmann
equation is solved to calculate the effective charge on a particle and a Donnan
approximation is used to derive the chemical potential and osmotic pressure in
the presence of salt. The coexistence data of lysozyme and silicotungstates are
analyzed within this scheme, especially with regard to the ionic-strength
dependence of the chemical potentials. The latter agree within the two phases
provided some upward adjustment of the effective charge is allowed for.Comment: 15 pages, 9 figure
Mesoscale simulations of surfactant dissolution and mesophase formation
The evolution of the contact zone between pure surfactant and solvent has
been studied by mesoscale simulation. It is found that mesophase formation
becomes diffusion controlled and follows the equilibrium phase diagram
adiabatically almost as soon as individual mesophases can be identified,
corresponding to times in real systems of order 10 microseconds.Comment: 4 pages, 2 figures, ReVTeX
Vapour-liquid coexistence in many-body dissipative particle dynamics
Many-body dissipative particle dynamics is constructed to exhibit
vapour-liquid coexistence, with a sharp interface, and a vapour phase of
vanishingly small density. In this form, the model is an unusual example of a
soft-sphere liquid with a potential energy built out of local-density dependent
one-particle self energies. The application to fluid mechanics problems
involving free surfaces is illustrated by simulation of a pendant drop.Comment: 8 pages, 6 figures, revtex
Polymers pushing Polymers: Polymer Mixtures in Thermodynamic Equilibrium with a Pore
We investigate polymer partitioning from polymer mixtures into nanometer size
cavities by formulating an equation of state for a binary polymer mixture
assuming that only one (smaller) of the two polymer components can penetrate
the cavity. Deriving the partitioning equilibrium equations and solving them
numerically allows us to introduce the concept of "polymers-pushing-polymers"
for the action of non-penetrating polymers on the partitioning of the
penetrating polymers. Polymer partitioning into a pore even within a very
simple model of a binary polymer mixture is shown to depend in a complicated
way on the composition of the polymer mixture and/or the pore-penetration
penalty. This can lead to enhanced as well as diminished partitioning, due to
two separate energy scales that we analyse in detail.Comment: 10 pages, 6 figure
SPEKTRALANALYTISCHE AUSWERTUNG SPANNUNGSOPTISCHER BILDER
Two hypotheses have been proposed about the etiology of neurodevelopmental learning disorders, such as dyslexia and dyscalculia: representation impairments and disrupted access to representations. We implemented a multi-method brain imaging approach to directly investigate these representation and access hypotheses in dyscalculia, a highly prevalent but understudied neurodevelopmental disorder in learning to calculate. We combined several magnetic resonance imaging methods and analyses, including univariate and multivariate analyses, functional and structural connectivity. Our sample comprised 24 adults with dyscalculia and 24 carefully matched controls. Results showed a clear deficit in the non-symbolic magnitude representations in parietal, temporal and frontal regions, as well as hyper-connectivity in visual brain regions in adults with dyscalculia. Dyscalculia in adults was thereby related to both impaired number representations and altered connectivity in the brain. We conclude that dyscalculia is related to impaired number representations as well as altered access to these representations.ISSN:1053-8119ISSN:1095-957
- …