Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Topological defect launches 3D mound in the active nematic sheet of
  neural progenitors   Cultured stem cells have become a standard platform not only for regenerative
medicine and developmental biology but also for biophysical studies. Yet, the
characterization of cultured stem cells at the level of morphology and
macroscopic patterns resulting from cell-to-cell interactions remain largely
qualitative, even though they are the simplest features observed in everyday
experiments. Here we report that neural progenitor cells (NPCs), which are
multipotent stem cells that give rise to cells in the central nervous system,
rapidly glide and stochastically reverse its velocity while locally aligning
with neighboring cells, thus showing features of an active nematic system.
Within the two-dimensional nematic pattern, we find interspaced topological
defects with +1/2 and -1/2 charges. Remarkably, we identified rapid cell
accumulation leading to three-dimensional mounds at the +1/2 topological
defects. Single-cell level imaging around the defects allowed quantification of
the evolving cell density, clarifying that not only cells concentrate at +1/2
defects, but also escape from -1/2 defects. We propose the mechanism of
instability around the defects as the interplay between the anisotropic
friction and the active force field, thus addressing a novel universal
mechanism for local cell density control.

29
The categories of this paper are: funct-an
6
The categories of this paper are: astro-ph
5
The categories of this paper are: gr-qc
11
The categories of this paper are: hep-lat
30
The categories of this paper are: q-alg
28
The categories of this paper are: alg-geom
37
The categories of this paper are: supr-con
15
The categories of this paper are: nucl-ex
23
The categories of this paper are: solv-int
0
The categories of this paper are: hep-ph
33
The categories of this paper are: plasm-ph
2
The categories of this paper are: math
13
The categories of this paper are: quant-ph
34
The categories of this paper are: chem-ph
25
The categories of this paper are: patt-sol
21
The categories of this paper are: adap-org