Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Foaming in stout beers   We review the differences between bubble formation in champagne and other
carbonated drinks, and stout beers which contain a mixture of dissolved
nitrogen and carbon dioxide. The presence of dissolved nitrogen in stout beers
gives them a number of properties of interest to connoisseurs and physicists.
These remarkable properties come at a price: stout beers do not foam
spontaneously and special technology, such as the widgets used in cans, is
needed to promote foaming. Nevertheless the same mechanism, nucleation by gas
pockets trapped in cellulose fibres, responsible for foaming in carbonated
drinks is active in stout beers, but at an impractically slow rate. This gentle
rate of bubble nucleation makes stout beers an excellent model system for the
scientific investigation of the nucleation of gas bubbles. The equipment needed
is very modest, putting such experiments within reach of undergraduate
laboratories. Finally we consider the suggestion that a widget could be
constructed by coating the inside of a beer can with cellulose fibres.

2
The categories of this paper are: math
19
The categories of this paper are: eess
31
The categories of this paper are: ao-sci
25
The categories of this paper are: patt-sol
7
The categories of this paper are: hep-th
1
The categories of this paper are: cs
34
The categories of this paper are: chem-ph
13
The categories of this paper are: quant-ph
22
The categories of this paper are: chao-dyn
30
The categories of this paper are: q-alg
16
The categories of this paper are: stat
24
The categories of this paper are: dg-ga
15
The categories of this paper are: nucl-ex
35
The categories of this paper are: mtrl-th
28
The categories of this paper are: alg-geom
9
The categories of this paper are: nlin