983 research outputs found
A new species of Archaeoryctes from the Middle Paleocene of China and the phylogenetic diversification of Didymoconidae
Didymoconidae are an enigmatic group of Asian endemic insectivorous mammals. We describe the new didymoconid species Archaeoryctes wangi sp. nov. from the Upper Member of the Wanghudun Formation (Middle Paleocene). This new species from the Qianshan Basin (Anhui Province, China) forms an interesting geographical intermediate between A. notialis from South China and A. borealis and A. euryalis from the Mongolian Plateau. To better understand the origin and evolutionary diversification of Didymoconidae, we performed a cladistic and stratocladistic study of the Didymoconidae and various outgroups. This study of dental material did not resolve the higher level affinities of Didymoconidae, but confirms the validity of the family and its distinctiveness from the morphologically similar Sarcodontidae. Moreover, our results corroborate the current didymoconid classification with the distinction of three subfamilies: “Ardynictinae”, Kennatheriinae and Didymoconinae; “Ardynictinae” are a paraphyletic stemgroup for the two other subfamilies. Our results suggest three distinct didymoconid radiations: (1) primitive ardynictines appeared in South China from the start of the Nongshanian; their evolution continues on the Mongolian Plateau with (2) the radiation of more evolved ardynictines and kennatheriines at the start of the Middle Eocene Arshantan and (3) the origin of didymoconines at the start of the Late Eocene Ergilian
How many weights can a cyclic code have ?
Upper and lower bounds on the largest number of weights in a cyclic code of
given length, dimension and alphabet are given. An application to irreducible
cyclic codes is considered. Sharper upper bounds are given for the special
cyclic codes (called here strongly cyclic), {whose nonzero codewords have
period equal to the length of the code}. Asymptotics are derived on the
function {that is defined as} the largest number of nonzero
weights a cyclic code of dimension over \F_q can have, and an algorithm
to compute it is sketched. The nonzero weights in some infinite families of
Reed-Muller codes, either binary or -ary, as well as in the -ary Hamming
code are determined, two difficult results of independent interest.Comment: submitted on 21 June, 201
LCD Codes from tridiagonal Toeplitz matrice
Double Toeplitz (DT) codes are codes with a generator matrix of the form
with a Toeplitz matrix, that is to say constant on the diagonals
parallel to the main. When is tridiagonal and symmetric we determine its
spectrum explicitly by using Dickson polynomials, and deduce from there
conditions for the code to be LCD. Using a special concatenation process, we
construct optimal or quasi-optimal examples of binary and ternary LCD codes
from DT codes over extension fields.Comment: 16 page
Red Queen Coevolution on Fitness Landscapes
Species do not merely evolve, they also coevolve with other organisms.
Coevolution is a major force driving interacting species to continuously evolve
ex- ploring their fitness landscapes. Coevolution involves the coupling of
species fit- ness landscapes, linking species genetic changes with their
inter-specific ecological interactions. Here we first introduce the Red Queen
hypothesis of evolution com- menting on some theoretical aspects and empirical
evidences. As an introduction to the fitness landscape concept, we review key
issues on evolution on simple and rugged fitness landscapes. Then we present
key modeling examples of coevolution on different fitness landscapes at
different scales, from RNA viruses to complex ecosystems and macroevolution.Comment: 40 pages, 12 figures. To appear in "Recent Advances in the Theory and
Application of Fitness Landscapes" (H. Richter and A. Engelbrecht, eds.).
Springer Series in Emergence, Complexity, and Computation, 201
The maximum number of minimal codewords in an code
Upper and lower bounds are derived for the quantity in the title, which is
tabulated for modest values of and An application to graphs with many
cycles is given.Comment: 6 pp. Submitte
Heating pulse tests under constant volume on natural Boom clay. Experimental results and numerical simulations
Boom clay is a potential geological host formation for High Level Nuclear Waste in Belgium. Impact of thermal loads may play an important role on this clay formation. To this aim, heating pulse tests on intact borehole samples were carried out using an axi-symmetric heating cell. Heating tests under nearly constant volume conditions and different target temperatures (maximum 85°C) were performed under controlled hydraulic boundary conditions. Selected test result are presented and afterwards calibrated and simulated using CODE_BRIGHT.Peer ReviewedPostprint (author’s final draft
Graph theoretic analysis of protein interaction networks of eukaryotes
Thanks to recent progress in high-throughput experimental techniques, the
datasets of large-scale protein interactions of prototypical multicellular
species, the nematode worm Caenorhabditis elegans and the fruit fly Drosophila
melanogaster, have been assayed. The datasets are obtained mainly by using the
yeast hybrid method, which contains false-positive and false-negative
simultaneously. Accordingly, while it is desirable to test such datasets
through further wet experiments, here we invoke recent developed network theory
to test such high throughput datasets in a simple way. Based on the fact that
the key biological processes indispensable to maintaining life are universal
across eukaryotic species, and the comparison of structural properties of the
protein interaction networks (PINs) of the two species with those of the yeast
PIN, we find that while the worm and the yeast PIN datasets exhibit similar
structural properties, the current fly dataset, though most comprehensively
screened ever, does not reflect generic structural properties correctly as it
is. The modularity is suppressed and the connectivity correlation is lacking.
Addition of interlogs to the current fly dataset increases the modularity and
enhances the occurrence of triangular motifs as well. The connectivity
correlation function of the fly, however, remains distinct under such interlogs
addition, for which we present a possible scenario through an in silico
modeling.Comment: 7 pages, 6 figures, 2 table
Critical Networks Exhibit Maximal Information Diversity in Structure-Dynamics Relationships
Network structure strongly constrains the range of dynamic behaviors
available to a complex system. These system dynamics can be classified based on
their response to perturbations over time into two distinct regimes, ordered or
chaotic, separated by a critical phase transition. Numerous studies have shown
that the most complex dynamics arise near the critical regime. Here we use an
information theoretic approach to study structure-dynamics relationships within
a unified framework and how that these relationships are most diverse in the
critical regime
Effect of edge removal on topological and functional robustness of complex networks
We study the robustness of complex networks subject to edge removal. Several
network models and removing strategies are simulated. Rather than the existence
of the giant component, we use total connectedness as the criterion of
breakdown. The network topologies are introduced a simple traffic dynamics and
the total connectedness is interpreted not only in the sense of topology but
also in the sense of function. We define the topological robustness and the
functional robustness, investigate their combined effect and compare their
relative importance to each other. The results of our study provide an
alternative view of the overall robustness and highlight efficient ways to
improve the robustness of the network models.Comment: 21 pages, 9 figure
Community-driven dispersal in an individual-based predator-prey model
We present a spatial, individual-based predator-prey model in which dispersal
is dependent on the local community. We determine species suitability to the
biotic conditions of their local environment through a time and space varying
fitness measure. Dispersal of individuals to nearby communities occurs whenever
their fitness falls below a predefined tolerance threshold. The spatiotemporal
dynamics of the model is described in terms of this threshold. We compare this
dynamics with the one obtained through density-independent dispersal and find
marked differences. In the community-driven scenario, the spatial correlations
in the population density do not vary in a linear fashion as we increase the
tolerance threshold. Instead we find the system to cross different dynamical
regimes as the threshold is raised. Spatial patterns evolve from disordered, to
scale-free complex patterns, to finally becoming well-organized domains. This
model therefore predicts that natural populations, the dispersal strategies of
which are likely to be influenced by their local environment, might be subject
to complex spatiotemporal dynamics.Comment: 43 pages, 7 figures, vocabulary modifications, discussion expanded,
references added, Ecological Complexity accepte
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