2,821 research outputs found
Zipping and collapse of diblock copolymers
Using exact enumeration methods and Monte Carlo simulations we study the
phase diagram relative to the conformational transitions of a two dimensional
diblock copolymer. The polymer is made of two homogeneous strands of monomers
of different species which are joined to each other at one end. We find that
depending on the values of the energy parameters in the model, there is either
a first order collapse from a swollen to a compact phase of spiral type, or a
continuous transition to an intermediate zipped phase followed by a first order
collapse at lower temperatures. Critical exponents of the zipping transition
are computed and their exact values are conjectured on the basis of a mapping
onto percolation geometry, thanks to recent results on path-crossing
probabilities.Comment: 12 pages, RevTeX and 14 PostScript figures include
A comparison of statistical models for short categorical or ordinal time series with applications in ecology
We study two statistical models for short-length categorical (or ordinal)
time series. The first one is a regression model based on generalized linear
model. The second one is a parametrized Markovian model, particularizing the
discrete autoregressive model to the case of categorical data. These models are
used to analyze two data-sets: annual larch cone production and weekly
planktonic abundance.Comment: 18 page
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