29 research outputs found
Cultural transmission and optimization dynamics
We study the one-dimensional version of Axelrod's model of cultural
transmission from the point of view of optimization dynamics. We show the
existence of a Lyapunov potential for the dynamics. The global minimum of the
potential, or optimum state, is the monocultural uniform state, which is
reached for an initial diversity of the population below a critical value.
Above this value, the dynamics settles in a multicultural or polarized state.
These multicultural attractors are not local minima of the potential, so that
any small perturbation initiates the search for the optimum state. Cultural
drift is modelled by such perturbations acting at a finite rate. If the noise
rate is small, the system reaches the optimum monocultural state. However, if
the noise rate is above a critical value, that depends on the system size,
noise sustains a polarized dynamical state.Comment: 11 pages, 10 figures include
Intracultural diversity in a model of social dynamics
We study the consequences of introducing individual nonconformity in social
interactions, based on Axelrod's model for the dissemination of culture. A
constraint on the number of situations in which interaction may take place is
introduced in order to lift the unavoidable ho mogeneity present in the final
configurations arising in Axelrod's related models. The inclusion of this
constraint leads to the occurrence of complex patterns of intracultural
diversity whose statistical properties and spatial distribution are
characterized by means of the concepts of cultural affinity and cultural cli
ne. It is found that the relevant quantity that determines the properties of
intracultural diversity is given by the fraction of cultural features that
characterizes the cultural nonconformity of individuals.Comment: 7 pages, 2 tables, 6 figure
Culture-area relation in Axelrod's model for culture dissemination
Axelrod's model for culture dissemination offers a nontrivial answer to the
question of why there is cultural diversity given that people's beliefs have a
tendency to become more similar to each other's as people interact repeatedly.
The answer depends on the two control parameters of the model, namely, the
number of cultural features that characterize each agent, and the number
of traits that each feature can take on, as well as on the size of the
territory or, equivalently, on the number of interacting agents. Here we
investigate the dependence of the number of distinct coexisting cultures on
the area in Axelrod's model -- the culture-area relationship -- through
extensive Monte Carlo simulations. We find a non-monotonous culture-area
relation, for which the number of cultures decreases when the area grows beyond
a certain size, provided that is smaller than a threshold value and . In the limit of infinite area, this threshold value
signals the onset of a discontinuous transition between a globalized regime
marked by a uniform culture (C=1), and a completely polarized regime where all
possible cultures coexist. Otherwise the culture-area relation
exhibits the typical behavior of the species-area relation, i.e., a
monotonically increasing curve the slope of which is steep at first and
steadily levels off at some maximum diversity value
Sequence homology in eukaryotes (SHOE): interactive visual tool for promoter analysis
Abstract Background Microarray and DNA-sequencing based technologies continue to produce enormous amounts of data on gene expression. This data has great potential to illuminate our understanding of biology and medicine, but the data alone is of limited value without computational tools to allow human investigators to visualize and interpret it in the context of their problem of interest. Results We created a web server called SHOE that provides an interactive, visual presentation of the available evidence of transcriptional regulation and gene co-expression to facilitate its exploration and interpretation. SHOE predicts the likely transcription factor binding sites in orthologous promoters of humans, mice, and rats using the combined information of 1) transcription factor binding preferences (position-specific scoring matrix (PSSM) libraries such as Transfac32, Jaspar, HOCOMOCO, ChIP-seq, SELEX, PBM, and iPS-reprogramming factor), 2) evolutionary conservation of putative binding sites in orthologous promoters, and 3) co-expression tendencies of gene pairs based on 1,714 normal human cells selected from the Gene Expression Omnibus Database. Conclusion SHOE enables users to explore potential interactions between transcription factors and target genes via multiple data views, discover transcription factor binding motifs on top of gene co-expression, and visualize genes as a network of gene and transcription factors on its native gadget GeneViz, the CellDesigner pathway analyzer, and the Reactome database to search the pathways involved. As we demonstrate here when using the CREB1 and Nf-κB datasets, SHOE can reliably identify experimentally verified interactions and predict plausible novel ones, yielding new biological insights into the gene regulatory mechanisms involved. SHOE comes with a manual describing how to run it on a local PC or via the Garuda platform (www.garuda-alliance.org), where it joins other popular gadgets such as the CellDesigner pathway analyzer and the Reactome database, as part of analysis workflows to meet the growing needs of molecular biologists and medical researchers. SHOE is available from the following URL http://ec2-54-150-223-65.ap-northeast-1.compute.amazonaws.com A video demonstration of SHOE can be found here: https://www.youtube.com/watch?v=qARinNb9Nt