Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Liquid-vapor oscillations of water in hydrophobic nanopores   Water plays a key role in biological membrane transport. In ion channels and
water-conducting pores (aquaporins), one dimensional confinement in conjunction
with strong surface effects changes the physical behavior of water. In
molecular dynamics simulations of water in short (0.8 nm) hydrophobic pores the
water density in the pore fluctuates on a nanosecond time scale. In long
simulations (460 ns in total) at pore radii ranging from 0.35 nm to 1.0 nm we
quantify the kinetics of oscillations between a liquid-filled and a
vapor-filled pore. This behavior can be explained as capillary evaporation
alternating with capillary condensation, driven by pressure fluctuations in the
water outside the pore. The free energy difference between the two states
depends linearly on the radius. The free energy landscape shows how a
metastable liquid state gradually develops with increasing radius. For radii
larger than ca. 0.55 nm it becomes the globally stable state and the vapor
state vanishes. One dimensional confinement affects the dynamic behavior of the
water molecules and increases the self diffusion by a factor of two to three
compared to bulk water. Permeabilities for the narrow pores are of the same
order of magnitude as for biological water pores. Water flow is not continuous
but occurs in bursts. Our results suggest that simulations aimed at collective
phenomena such as hydrophobic effects may require simulation times longer than
50 ns. For water in confined geometries, it is not possible to extrapolate from
bulk or short time behavior to longer time scales.

5
The categories of this paper are: gr-qc
32
The categories of this paper are: atom-ph
24
The categories of this paper are: dg-ga
13
The categories of this paper are: quant-ph
23
The categories of this paper are: solv-int
9
The categories of this paper are: nlin
29
The categories of this paper are: funct-an
12
The categories of this paper are: nucl-th
33
The categories of this paper are: plasm-ph
26
The categories of this paper are: bayes-an
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The categories of this paper are: patt-sol
19
The categories of this paper are: eess
34
The categories of this paper are: chem-ph
31
The categories of this paper are: ao-sci
11
The categories of this paper are: hep-lat
6
The categories of this paper are: astro-ph