Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Surfactant-assisted spreading of an oil-in-water emulsion on the surface
  of a liquid bath   This fluid dynamics video shows how an oil-in-water emulsion stabilized by an
ionic surfactant spreads on the free surface of a layer of pure water. The
spreading shows two intriguing features: a transparent area surrounding the
source of oil droplets, and a fast retraction of the layer of oil droplets on
itself once the source has emptied. We show that the dynamics of spreading are
strongly connected to the interfacial/bulk properties of the surfactant.

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The categories of this paper are: astro-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: hep-ph
1
The categories of this paper are: cs
23
The categories of this paper are: solv-int
5
The categories of this paper are: gr-qc
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The categories of this paper are: ao-sci
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The categories of this paper are: hep-lat
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The categories of this paper are: nlin
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The categories of this paper are: cond-mat
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The categories of this paper are: math-ph
21
The categories of this paper are: adap-org
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The categories of this paper are: cmp-lg
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-th
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The categories of this paper are: chem-ph