Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magnetic Chains Created by Polymer-Induced Assembly of Hollow Cobalt
  Nanoparticles   Magnetic chains of hollow cobalt nanoparticles (450-750 nm) have been
synthesized by using poly(vinyl pyrrolidone) (PVP) as a template in an ethylene
glycol solution. In this process, CoCl2.6H2O was reduced by N2H4.H2O in the
presence of PVP. All of the Co nanoparticles are hollow with a shell of 40 nm
and self-assembled into a chainlike structure that is as long as ~10 micron. At
300 K, the branched hollow Co nanoparticle chains exhibit a saturation
magnetization of 37.5 emu/g, a remnant magnetization of approximately 1.55
emu/g, and a coercivity of about 66 Oe, which is more than an order of
magnitude larger than that of the bulk

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The categories of this paper are: funct-an
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The categories of this paper are: patt-sol
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The categories of this paper are: bayes-an
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-th
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The categories of this paper are: dg-ga
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The categories of this paper are: alg-geom
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The categories of this paper are: physics
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The categories of this paper are: eess
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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: hep-ex
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The categories of this paper are: adap-org
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The categories of this paper are: ao-sci
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The categories of this paper are: cs
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The categories of this paper are: math