Instruct: Identify the main and secondary category of Arxiv papers based on the titles
Query: Repeated Acoustic Vaporization of Perfluorohexane Nanodroplets for
  Contrast-Enhanced Ultrasound Imaging
7
The categories of this paper are: hep-th
5
The categories of this paper are: gr-qc
25
The categories of this paper are: patt-sol
18
The categories of this paper are: econ
8
The categories of this paper are: hep-ex
24
The categories of this paper are: dg-ga
0
The categories of this paper are: hep-ph
28
The categories of this paper are: alg-geom
26
The categories of this paper are: bayes-an
23
The categories of this paper are: solv-int
30
The categories of this paper are: q-alg
15
The categories of this paper are: nucl-ex
17
The categories of this paper are: q-fin
35
The categories of this paper are: mtrl-th
9
The categories of this paper are: nlin
10
The categories of this paper are: q-bio