Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Formation and Rupture of Ca$^{2+}$ Induced Pectin Biopolymer Gels   When calcium salts are added to an aqueous solution of polysaccharide pectin,
ionic cross-links form between pectin chains, giving rise to a gel network in
dilute solution. In this work, dynamic light scattering (DLS) is employed to
study the microscopic dynamics of the fractal aggregates (flocs) that
constitute the gels, while rheological measurements are performed to study the
process of gel rupture. As calcium salt concentration is increased, DLS
experiments reveal that the polydispersities of the flocs increase
simultaneously with the characteristic relaxation times of the gel network.
Above a critical salt concentration, the flocs become interlinked to form a
reaction-limited fractal gel network. Rheological studies demonstrate that the
limits of the linear rheological response and the critical stresses required to
rupture these networks both decrease with increase in salt concentration. These
features indicate that the ion-mediated pectin gels studied here lie in a
`strong link' regime that is characterised by inter-floc links that are
stronger than intra-floc links. A scaling analysis of the experimental data
presented here demonstrates that the elasticities of the individual fractal
flocs exhibit power-law dependences on the added salt concentration. We
conclude that when pectin and salt concentrations are both increased, the
number of fractal flocs of pectin increases simultaneously with the density of
crosslinks, giving rise to very large values of the bulk elastic modulus.

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The categories of this paper are: supr-con
8
The categories of this paper are: hep-ex
5
The categories of this paper are: gr-qc
25
The categories of this paper are: patt-sol
15
The categories of this paper are: nucl-ex
34
The categories of this paper are: chem-ph
11
The categories of this paper are: hep-lat
28
The categories of this paper are: alg-geom
7
The categories of this paper are: hep-th
16
The categories of this paper are: stat
14
The categories of this paper are: math-ph
10
The categories of this paper are: q-bio
12
The categories of this paper are: nucl-th
23
The categories of this paper are: solv-int
29
The categories of this paper are: funct-an
0
The categories of this paper are: hep-ph