Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: New ultrasmall iron-oxide nanoparticles with high magnetisation as
  potential T1-MRI contrast agents for Molecular Imaging   Here we report on the synthesis of very small gamma-Fe2O3 nanoparticles (5
nm) presenting very narrow particle size distribution and exceptionally high
saturation magnetisation. The synthesis has been carried out in an organic
medium with subsequent transfer to an aqueous solution at physiological pH. The
structural and magnetic properties were kept unaltered after the solvent
exchange. NMR relaxometric measurements show the potential of these particles
as specific reporters for magnetic resonance molecular imaging.

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The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-th
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The categories of this paper are: q-fin
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The categories of this paper are: eess
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The categories of this paper are: q-alg
3
The categories of this paper are: physics
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The categories of this paper are: econ
9
The categories of this paper are: nlin
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The categories of this paper are: bayes-an
7
The categories of this paper are: hep-th
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The categories of this paper are: acc-phys
2
The categories of this paper are: math
13
The categories of this paper are: quant-ph
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The categories of this paper are: solv-int
8
The categories of this paper are: hep-ex
24
The categories of this paper are: dg-ga