Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Tailored nanodiamonds for hyperpolarized 13C MRI   Nanodiamond is poised to become an attractive material for hyperpolarized 13C
MRI if large nuclear polarizations can be achieved without the accompanying
rapid spin-relaxation driven by paramagnetic species. Here we report enhanced
and long-lived 13C polarization in synthetic nanodiamonds tailored by
acid-cleaning and air-oxidation protocols. Our results separate the
contributions of different paramagnetic species on the polarization behavior,
identifying the importance of substitutional nitrogen defect centers in the
nanodiamond core. These results are likely of use in the development of
nanodiamond-based imaging agents with size distributions of relevance for
examining biological processes.

6
The categories of this paper are: astro-ph
33
The categories of this paper are: plasm-ph
23
The categories of this paper are: solv-int
15
The categories of this paper are: nucl-ex
1
The categories of this paper are: cs
30
The categories of this paper are: q-alg
19
The categories of this paper are: eess
12
The categories of this paper are: nucl-th
37
The categories of this paper are: supr-con
18
The categories of this paper are: econ
34
The categories of this paper are: chem-ph
29
The categories of this paper are: funct-an
5
The categories of this paper are: gr-qc
26
The categories of this paper are: bayes-an
28
The categories of this paper are: alg-geom
2
The categories of this paper are: math