17,662 research outputs found
Confined water in the low hydration regime
Molecular dynamics results on water confined in a silica pore in the low
hydration regime are presented. Strong layering effects are found due to the
hydrophilic character of the substrate. The local properties of water are
studied as function of both temperature and hydration level. The interaction of
the thin films of water with the silica atoms induces a strong distortion of
the hydrogen bond network. The residence time of the water molecules is
dependent on the distance from the surface. Its behavior shows a transition
from a brownian to a non-brownian regime approaching the substrate in agreement
with results found in studies of water at contact with globular proteins.Comment: 7 pages with 12 figures (RevTeX4). To be published on J. Chem. Phy
Modifications of the hydrogen bond network of liquid water in a cylindrical SiO_2 pore
We present results of molecular dynamics simulations of water confined in a
silica pore. A cylindrical cavity is created inside a vitreous silica cell with
geometry and size similar to the pores of real Vycor glass. The simulations are
performed at different hydration levels. At all hydration levels water adsorbs
strongly on the Vycor surface; a double layer structure is evident at higher
hydrations. At almost full hydration the modifications of the
confinement-induced site-site pair distribution functions are in qualitative
agreement with neutron diffraction experiment. A decrease in the number of
hydrogen bonds between water molecules is observed along the pore radius, due
to the tendency of the molecules close to the substrate to form hydrogen-bonds
with the hydrophilic pore surface. As a consequence we observe a substrate
induced distortion of the H-bond tetrahedral network of water molecules in the
regions close to the surface.Comment: Talk presented at "Physics of Liquids: Foundations, Highlights,
Challenge", Murau Sept. 1998. To appear in J. Mol. Li
Strongly magnetized iron white dwarfs and the total lepton number violation
The influence of a neutrinoless electron to positron conversion on a cooling
of strongly magnetized iron white dwarfs is studied.Comment: 4 pages, contribution to the conference MEDEX'13, Prague, June 11-14,
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