1,836 research outputs found
Simply connected Alexandrov 4-manifolds with positive or nonnegative curvature and torus actions
We point out that a 4-dimensional topological manifold with an Alexandrov
metric (of curvature bounded below) and with an effective, isometric action of
the circle or the 2-torus is locally smooth. This observation implies that the
topological and equivariant classifications of compact, simply connected
Riemannian 4-manifolds with positive or nonnegative sectional curvature and an
effective isometric action of a circle or a 2-torus also hold if we consider
Alexandrov manifolds instead of Riemannian manifolds.Comment: 10 pages, title changed, results are now proved for Alexandrov
4-manifolds, added examples, simplified proof
Hydrogen bonds and asymmetrical heat diffusion in a-Helices. A Computational Analysis
In this work, we report the heat rectifying capability of a-helices. Using
molecular dynamics simulations we show an increased thermal diffusivity in the
C-Terminal to N-Terminal direction of propagation. The origin of this effect
seems to be a function of the particular orientation of the hydrogen bonds
stabilizing these a-helices. Our results may be relevant for the design of
thermal rectification devices for materials science and lend support to the
role of normal length hydrogen bonds in the asymmetrical energy flow in
proteins
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