Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ultra-Thin Double-Walled Carbon Nanotubes A Novel Nanocontainer for
  Preparing Atomic Wires   Double-walled carbon nanotubes (DWCNTs) with high graphitization have been
synthesized by hydrogen arc discharge. The obtained DWCNTs have a narrow
distribution of diameters of both the inner and outer tubes, and more than half
of the DWCNTs have inner diameters in the range 0.6-1.0 nm. Field electron
emission from a DWCNT cathode to an anode has been measured, and the emission
current density of DWCNTs reached 1 A/cm2 at an applied field of about 4.3
V/{\mu}m. After high-temperature treatment of DWCNTs, long linear carbon chains
(C-chains) can be grown inside the ultra-thin DWCNTs to form a novel
C-chain@DWCNT nanostructure, showing that these ultra-thin DWCNTs are an
appropriate nanocontainer for preparing truly one-dimensional nanostructures
with one-atom-diameter.

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The categories of this paper are: atom-ph
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The categories of this paper are: eess
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The categories of this paper are: supr-con
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The categories of this paper are: math-ph
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The categories of this paper are: adap-org
16
The categories of this paper are: stat
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The categories of this paper are: comp-gas
3
The categories of this paper are: physics
6
The categories of this paper are: astro-ph
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The categories of this paper are: q-alg
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The categories of this paper are: solv-int
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The categories of this paper are: nucl-ex
0
The categories of this paper are: hep-ph
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The categories of this paper are: ao-sci
5
The categories of this paper are: gr-qc
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The categories of this paper are: hep-th