Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Sedimentation and diffusion of passive particles in suspensions of
  swimming Escherichia coli   Sedimentation in active fluids has come into focus due to the ubiquity of
swimming micro-organisms in natural and artificial environments. Here, we
experimentally investigate sedimentation of passive particles in water
containing various concentrations of the bacterium E. coli. Results show that
the presence of living bacteria reduces the velocity of the sedimentation front
even in the dilute regime, where the sedimentation velocity is expected to be
independent of particle concentration. Bacteria increase the effective
diffusion coefficient of the passive particles, which determines the width of
the sedimentation front. For higher bacteria concentration, we find the
development of two sedimentation fronts due to bacterial death. A model in
which an advection-diffusion equation describing the settling of particles
under gravity is coupled to the population dynamics of the bacteria seems to
capture the experimental trends relatively well.

19
The categories of this paper are: eess
34
The categories of this paper are: chem-ph
0
The categories of this paper are: hep-ph
1
The categories of this paper are: cs
26
The categories of this paper are: bayes-an
10
The categories of this paper are: q-bio
5
The categories of this paper are: gr-qc
8
The categories of this paper are: hep-ex
20
The categories of this paper are: acc-phys
18
The categories of this paper are: econ
27
The categories of this paper are: comp-gas
14
The categories of this paper are: math-ph
6
The categories of this paper are: astro-ph
23
The categories of this paper are: solv-int
11
The categories of this paper are: hep-lat
22
The categories of this paper are: chao-dyn