7,695 research outputs found
Optimal prediction of folding rates and transition state placement from native state geometry
A variety of experimental and theoretical studies have established that the
folding process of monomeric proteins is strongly influenced by the topology of
the native state. In particular, folding times have been shown to correlate
well with the contact order, a measure of contact locality. Our investigation
focuses on identifying additional topologic properties that correlate with
experimentally measurable quantities, such as folding rates and transition
state placement, for both two- and three-state folders. The validation against
data from forty experiments shows that a particular topologic property which
measures the interdepedence of contacts, termed cliquishness or clustering
coefficient, can account with significant accuracy both for the transition
state placement and especially for folding rates, the linear correlation
coefficient being . This result can be further improved to , by
optimally combining the distinct topologic information captured by cliquishness
and contact order.Comment: Revtex, 15 pages, 8 figure
A clustering algorithm for multivariate data streams with correlated components
Common clustering algorithms require multiple scans of all the data to
achieve convergence, and this is prohibitive when large databases, with data
arriving in streams, must be processed. Some algorithms to extend the popular
K-means method to the analysis of streaming data are present in literature
since 1998 (Bradley et al. in Scaling clustering algorithms to large databases.
In: KDD. p. 9-15, 1998; O'Callaghan et al. in Streaming-data algorithms for
high-quality clustering. In: Proceedings of IEEE international conference on
data engineering. p. 685, 2001), based on the memorization and recursive update
of a small number of summary statistics, but they either don't take into
account the specific variability of the clusters, or assume that the random
vectors which are processed and grouped have uncorrelated components.
Unfortunately this is not the case in many practical situations. We here
propose a new algorithm to process data streams, with data having correlated
components and coming from clusters with different covariance matrices. Such
covariance matrices are estimated via an optimal double shrinkage method, which
provides positive definite estimates even in presence of a few data points, or
of data having components with small variance. This is needed to invert the
matrices and compute the Mahalanobis distances that we use for the data
assignment to the clusters. We also estimate the total number of clusters from
the data.Comment: title changed, rewritte
Low energy solutions for singularly perturbed coupled nonlinear systems on a Riemannian manifold with boundary
Let (M,g) be asmooth, compact Riemannian manifold with smooth boundary, with
n= dim M= 2,3. We suppose the boundary of M to be a smooth submanifold of M
with dimension n-1. We consider a singularly perturbed nonlinear system, namely
Klein-Gordon-Maxwell-Proca system, or Klein-Gordon-Maxwell system of
Scrhoedinger-Maxwell system on M. We prove that the number of low energy
solutions, when the perturbation parameter is small, depends on the topological
properties of the boundary of M, by means of the Lusternik Schnirelmann
category. Also, these solutions have a unique maximum point that lies on the
boundary
Non degeneracy of critical points of the Robin function with respect to deformations of the domain
We show a result of genericity for non degenerate critical points of the
Robin function with respect to deformations of the domai
A multiplicity result for double singularly perturbed elliptic systems
We show that the number of low energy solutions of a double singularly
perturbed Schroedinger Maxwell system type on a smooth 3 dimensional manifold
(M,g) depends on the topological properties of the manifold. The result is
obtained via Lusternik Schnirelmann category theory
Probing the entanglement and locating knots in ring polymers: a comparative study of different arc closure schemes
The interplay between the topological and geometrical properties of a polymer
ring can be clarified by establishing the entanglement trapped in any portion
(arc) of the ring. The task requires to close the open arcs into a ring, and
the resulting topological state may depend on the specific closure scheme that
is followed. To understand the impact of this ambiguity in contexts of
practical interest, such as knot localization in a ring with non trivial
topology, we apply various closure schemes to model ring polymers. The rings
have the same length and topological state (a trefoil knot) but have different
degree of compactness. The comparison suggests that a novel method, termed the
minimally-interfering closure, can be profitably used to characterize the arc
entanglement in a robust and computationally-efficient way. This closure method
is finally applied to the knot localization problem which is tackled using two
different localization schemes based on top-down or bottom-up searches.Comment: 9 pages, 7 figures. Submitted to Progress of Theoretical Physic
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