19,249 research outputs found
Hydrodynamic interactions of spherical particles in suspensions confined between two planar walls
Hydrodynamic interactions in a suspension of spherical particles confined
between two parallel planar walls are studied under creeping-flow conditions.
The many-particle friction matrix in this system is evaluated using our novel
numerical algorithm based on transformations between Cartesian and spherical
representations of Stokes flow. The Cartesian representation is used to
describe the interaction of the fluid with the walls and the spherical
representation is used to describe the interaction with the particles. The
transformations between these two representations are given in a closed form,
which allows us to evaluate the coefficients in linear equations for the
induced-force multipoles on particle surfaces. The friction matrix is obtained
from these equations, supplemented with the superposition lubrication
corrections. We have used our algorithm to evaluate the friction matrix for a
single sphere, a pair of spheres, and for linear chains of spheres. The
friction matrix exhibits a crossover from a quasi-two-dimensional behavior (for
systems with small wall separation H) to the three-dimensional behavior (when
the distance H is much larger than the interparticle distance L). The crossover
is especially pronounced for a long chain moving in the direction normal to its
orientation and parallel to the walls. In this configuration, a large pressure
buildup occurs in front of the chain for small values of the gapwidth H, which
results in a large hydrodynamic friction force. A standard wall superposition
approximation does not capture this behavior
Relative phases in Dalitz plot amplitudes for and
Relative phases of amplitudes for meson decays to a light pseudoscalar
meson and a light vector meson decaying to two pseudoscalar mesons will
lead to characteristic interferences on the three-body Dalitz plot. These
phases may be compared with predictions of a flavor-symmetric treatment which
extracts contributing amplitudes and their relative phases from a fit to decay rates. Good agreement was found previously for the cases of and . The present work is devoted
to the decays and , for which
agreement is not found. Several suggestions are offered for this discrepancy.Comment: 11 pages, 3 figures, to be published in Phys. Rev. D. Additonal
figure, text, and references; minor correction
The cD galaxy in Abell cluster 1775
Over the last 20 years, a number of workers have studied the multiple nuclei cD galaxy in the rich Abell cluster 1775, trying to discover its nature. In all the cases though, very little has been published concerning its morphology. The majority of arguments about the nature of this object have been based on the relative radial velocities of the 2 components with each other and with the other galaxies in the cluster, or its radio morphology. Very little work has been done on the optical morphology. To rectify that lack of data, the authors have obtained charge coupled device (CCD) images of the cD. The authors find from the CCD data that the cD is unlikely to be a bound object and that there is strong evidence for a collision
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