Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Isotopic abundances of carbon and nitrogen in Jupiter-family and Oort
  Cloud comets   The 12C14N/12C15N and 12C14N/13C14N isotopic ratios are determined for the
first time in a Jupiter-family comet, 88P/1981 Q1 Howell, and in the chemically
peculiar Oort Cloud comet C/1999 S4 (LINEAR). By comparing these measurements
to previous ones derived for six other Oort Cloud comets (including one of
Halley-type), we find that both the carbon and nitrogen isotopic ratios are
constant within the uncertainties. The mean values are 12C/13C ~ 90 and 14N/15N
\~ 145 for the eight comets. These results strengthen the view that CN radicals
originate from refractory organics formed in the protosolar molecular cloud and
subsequently incorporated in comets.

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The categories of this paper are: q-bio
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The categories of this paper are: adap-org
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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: hep-th
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The categories of this paper are: patt-sol
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The categories of this paper are: acc-phys
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The categories of this paper are: supr-con
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The categories of this paper are: solv-int
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The categories of this paper are: quant-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: chem-ph
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The categories of this paper are: hep-lat
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The categories of this paper are: math-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: physics