Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The N/O abundance ratio in the lowest-metallicity blue compact dwarf
  galaxies   The results of the N/O abundance determination in a sample of low-metallicity
blue compact dwarf (BCD) galaxies based on new spectroscopic observations with
large telescopes (Keck, VLT, MMT, 4m KPNO) are presented. We show that the N/O
abundance ratio is constant at lowest metallicities < Zsun/20, confirming
previous findings and strongly supporting the origin of nitrogen as a primary
element.

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The categories of this paper are: eess
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The categories of this paper are: plasm-ph
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The categories of this paper are: chem-ph
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The categories of this paper are: math-ph
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The categories of this paper are: econ
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The categories of this paper are: atom-ph
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The categories of this paper are: stat
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The categories of this paper are: physics
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The categories of this paper are: alg-geom
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The categories of this paper are: acc-phys
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The categories of this paper are: mtrl-th
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The categories of this paper are: adap-org
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The categories of this paper are: solv-int
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The categories of this paper are: q-fin
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The categories of this paper are: nucl-ex
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The categories of this paper are: hep-ph