21,876 research outputs found
Why are Fluid Densities So Low in Carbon Nanotubes?
The equilibrium density of fluids under nanoconfinement can differ
substantially from their bulk density. Using a mean-field approach to describe
the energetic landscape near the carbon nanotube (CNT) wall, we obtain
analytical results describing the lengthscales associated with the layering
observed at the fluid-CNT interface. When combined with molecular simulation
results for the fluid density in the layered region, this approach allows us to
derive a closed-form prediction for the overall equilibrium fluid density as a
function of the CNT radius that is in excellent agreement with molecular
dynamics simulations. We also show how aspects of this theory can be extended
to describe water confined within CNTs and find good agreement with results
from the literature
Momentum conservation and correlation analyses in heavy-ion collisions at ultrarelativistic energies
Global transverse-momentum conservation induces correlations between any
number of particles, which contribute in particular to the two- and
three-particle correlations measured in heavy-ion collisions. These
correlations are examined in detail, and their importance for studies of jets
and their interaction with the medium is discussed.Comment: 5 pages, 2 figures. v2: corrected typos and added a paragrap
Numerical determination of the effective moments of non-spherical particles
Dielectric characterisation of polarisable particles, and prediction of the forces and torques exerted upon them, relies on the knowledge of the effective, induced dipole moment. In turn, through the mechanism of depolarisation, the induced dipole moment of a particle is strongly dependent upon its shape. Since realistic shapes create modelling difficulties, the âspherical particleâ approximation is often invoked. However, in many cases, including biological dielectric spectroscopy and dielectrophoresis, this assumption is a poor one. For example, human erythrocytes are essentially oblate spheroids with indented sides, while viruses and bacteria often have elongated cigar shapes. Since shape-dependent polarisation both strongly influences the accuracy of conventional dielectric characterisation methods using Maxwellâs mixture formula and confounds accurate prediction of dielectrophoretic forces and torques, it is important to develop means to treat non-spherical particles. In this paper, we demonstrate a means to extract the dipole moment directly from numerical solutions of the induced electrostatic potential when a particle is placed in a uniform electric field. The accuracy of the method is demonstrated for a range of particle shapes: spherical, ellipsoidal, truncated cylinders and an approximation of an erythrocyte, the red blood cell
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