Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Screening lengths and osmotic compressibility of flexible
  polyelectrolytes in excess salt solutions   We report results of small angle neutron scattering measurements made on
sodium polystyrene sulfonate in aqueous salt solutions. The correlation length
and osmotic compressibility are measured as a function of polymer (c) and added
salt ($c_S$) concentrations, and the results are compared with scaling
predictions and the random-phase approximation (RPA). In Dobrynin et al's
scaling model the osmotic pressure consists of a counter-ion contribution and a
polymer contribution. The polymer contribution is found to be two orders of
magnitude smaller than expected from the scaling model, in agreement with
earlier observations made on neutral polymers in good solvent condition. RPA
allows the determination of single-chain dimensions in semidilute solutions at
high polymer and added salt concentrations, but fails for $c_S < 2$ M. The \chi
parameter can be modelled as the sum of an intrinsic contribution and an
electrostatic term: $\chi \simeq \chi0+K/c_S^{1/2}$, where $\chi_0 > 0.5$ is
consistent with the hydrophobic nature of the backbone of NaPSS. The dependence
of $\chi_{elec} \simeq 1/c_S^{1/2}$ disagrees with the random-phase
approximation ($\chi_{elec} \simeq 1/c_S$), but agrees with the light
scattering results in dilute solution and Dobrynin et al's scaling treatment of
electrostatic excluded volume.

11
The categories of this paper are: hep-lat
20
The categories of this paper are: acc-phys
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The categories of this paper are: q-fin
35
The categories of this paper are: mtrl-th
8
The categories of this paper are: hep-ex
21
The categories of this paper are: adap-org
29
The categories of this paper are: funct-an
1
The categories of this paper are: cs
30
The categories of this paper are: q-alg
7
The categories of this paper are: hep-th
23
The categories of this paper are: solv-int
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The categories of this paper are: math-ph
28
The categories of this paper are: alg-geom
15
The categories of this paper are: nucl-ex
33
The categories of this paper are: plasm-ph
0
The categories of this paper are: hep-ph