Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Does avian magnetoreception rely on both magnetite and maghemite?   Recently, a putative magnetoreceptor in the upper-beak skin of homing pigeons
was chemically characterized using X-ray flourescence and absorbtion studies
[Fleissner et al., 2007. A novel concept of Fe-mineral based magnetoreception:
histological and physiochemical data from the upper beak of homing pigeons.
Naturwissenschaften 94 (8), 631-642]. In this short communication we point out
that the novel concept propagated is based on conclusions that are not
supported by data and, in fact, stand in contradiction to previously published
crystallographic and magnetic data.

5
The categories of this paper are: gr-qc
25
The categories of this paper are: patt-sol
34
The categories of this paper are: chem-ph
31
The categories of this paper are: ao-sci
23
The categories of this paper are: solv-int
13
The categories of this paper are: quant-ph
10
The categories of this paper are: q-bio
32
The categories of this paper are: atom-ph
15
The categories of this paper are: nucl-ex
4
The categories of this paper are: cond-mat
14
The categories of this paper are: math-ph
0
The categories of this paper are: hep-ph
7
The categories of this paper are: hep-th
8
The categories of this paper are: hep-ex
16
The categories of this paper are: stat
21
The categories of this paper are: adap-org