69,346 research outputs found
The Most âSignificant Relationshipâ in the Conflicts Law of TortsâLaw and Reason Versus the Restatement Second
Binary central stars of planetary nebulae
This paper reviews our knowledge on binary central stars of planetary nebulae
and presents some personal opinions regarding their evolution. Three types of
interactions are distinguished: type I, where the binary companion induces the
mass loss; type II, where it shapes the mass loss but does not enhance it; type
III, where a wide orbit causes the centre of mass to move, leading to a spiral
embedded in the wind. Surveys for binary central stars are discussed, and the
separations are compared to the distribution for binary post-AGB stars. The
effect of close binary evolution on nebular morphology is discussed.
Post-common-envelope binaries are surrounded by thin, expanding disks, expelled
in the orbital plane. Wider binaries give rise to much thicker expanding torii.
Type I binary evolution predicts a wide distribution of masses of central
stars, skewed towards low masses. Comparison with observed mass distributions
suggests that this is unlikely to be the only channel leading to the formation
of a planetary nebula. A new sample of compact Bulge nebulae shows about 40% of
nebulae with binary-induced morphologies.Comment: Invited review, in 'Evolution and chemistry of symbiotic stars and
related objects', Wierzba, August 2006. To appear in Baltic Astronom
The Immunity of Polymer-Microemulsion Networks
The concept of network immunity, i.e., the robustness of the network
connectivity after a random deletion of edges or vertices, has been
investigated in biological or communication networks. We apply this concept to
a self-assembling, physical network of microemulsion droplets connected by
telechelic polymers, where more than one polymer can connect a pair of
droplets. The gel phase of this system has higher immunity if it is more likely
to survive (i.e., maintain a macroscopic, connected component) when some of the
polymers are randomly degraded. We consider the distribution of the
number of polymers between a pair of droplets, and show that gel immunity
decreases as the variance of increases. Repulsive interactions
between the polymers decrease the variance, while attractive interactions
increase the variance, and may result in a bimodal .Comment: Corrected typo
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