40,268 research outputs found
A Characterization of the Degree Sequences of 2-Trees
A graph G is a 2-tree if G=K_3, or G has a vertex v of degree 2, whose
neighbours are adjacent, and G\v{i}s a 2-tree. A characterization of the degree
sequences of 2-trees is given. This characterization yields a linear-time
algorithm for recognizing and realizing degree sequences of 2-trees.Comment: 17 pages, 5 figure
Characterizing perfect recall using next-step temporal operators in S5 and sub-S5 Epistemic Temporal Logic
We review the notion of perfect recall in the literature on interpreted
systems, game theory, and epistemic logic. In the context of Epistemic Temporal
Logic (ETL), we give a (to our knowledge) novel frame condition for perfect
recall, which is local and can straightforwardly be translated to a defining
formula in a language that only has next-step temporal operators. This frame
condition also gives rise to a complete axiomatization for S5 ETL frames with
perfect recall. We then consider how to extend and consolidate the notion of
perfect recall in sub-S5 settings, where the various notions discussed are no
longer equivalent
Gibbs fragmentation trees
We study fragmentation trees of Gibbs type. In the binary case, we identify
the most general Gibbs-type fragmentation tree with Aldous' beta-splitting
model, which has an extended parameter range with respect to the
probability distributions on which it is based.
In the multifurcating case, we show that Gibbs fragmentation trees are
associated with the two-parameter Poisson--Dirichlet models for exchangeable
random partitions of , with an extended parameter range
, and , , .Comment: Published in at http://dx.doi.org/10.3150/08-BEJ134 the Bernoulli
(http://isi.cbs.nl/bernoulli/) by the International Statistical
Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm
Recent transmission clustering of HIV-1 C and CRF17_BF strains characterized by NNRTI-related mutations among newly diagnosed men in central Italy
Increased evidence of relevant HIV-1 epidemic transmission in European countries is being reported, with an increased circulation of non-B-subtypes. Here, we present two recent HIV-1 non-B transmission clusters characterized by NNRTI-related amino-acidic mutations among newly diagnosed HIV-1 infected men, living in Rome (Central-Italy)
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