Dipsadidae is the most diversified family of snakes, composed of species showing an impressive variety of color patterns. Some species are cryptic whereas others have contrasting patterns comprised by bright colors alternated with darker shades, including particular combinations of vivid colors characteristic of coral snakes (Elapidae). Species with such patterns are thought to be mimics of cor...

Drosophila melanogaster is widely used as a model in DNA variation studies. Patterns of polymorphism have, however, been affected by the history of this species, which is thought to have recently spread out of Africa to the rest of the world. We analyzed DNA sequence variation in 11 populations, including four continental African and seven non-African samples (including Madagascar), at four ind...

Let C(T) denote the poset of subtrees of a tree T with respect to the inclusion ordering. Jacobson, Kézdy and Seif gave a single example of a tree T for which C(T) is not Sperner, answering a question posed by Penrice. The authors then ask whether there exist an infinite family of trees T such that C(T) is not Sperner. This paper provides such a family.

1. Predators often prey on individuals that are sick or otherwise weakened. Although previous studies have shown higher abundance of parasites in prey, whether prey have elevated loads of micro-organisms remains to be determined. 2. We quantified the abundance of bacteria and fungi on feathers of woodpigeons Columba palumbus L., jays Garrulus glandarius L. and blackbirds Turdus merula L. that e...

We prove that there exist natural generalizations of the classical bootstrap percolation model on Z that have non-trivial critical probabilities, and moreover we characterize all homogeneous, local, monotone models with this property. Van Enter [28] (in the case d = r = 2) and Schonmann [25] (for all d > r > 2) proved that r-neighbour bootstrap percolation models have trivial critical probabili...

Globally coherent patterns of phase can be obscured by analysis techniques that aggregate brain activity measures across-trials, whether prior to source localization or for estimating inter-areal coherence. We analyzed, at single-trial level, whole head MEG recorded during an observer-triggered apparent motion task. Episodes of globally coherent activity occurred in the delta, theta, alpha and ...

If φ is a nontrivial automorphism of a thick building ∆ of purely infinite type, we prove that there is no bound on the distance that φ moves a chamber. This has the following group-theoretic consequence: If G is a group of automorphisms of ∆ with bounded quotient, then the center of G is trivial.

The panel on uncertain reasoning at AAAI-84 considered the question of whether or not implementations of non-monotonic reasoning should be probabilistic. A variety of (generally unsupported) claims were made to the effect that probabilities arc unintuitive, that the numbers needed arc unavailable, and that the method generally is inappropriate. The counterclaims that probabilities are intuit iv...

We give several pieces of evidence to show that extremal black holes cannot be obtained as limits of non-extremal black holes. We review arguments in the literature showing that the entropy of extremal black holes is zero, while that of near-extremal ones obey the Bekenstein-Hawking formula. However, from the counting of degeneracy of quantum (BPS) states of string theory the entropy of extrema...