Biomedical subjects

Kevin E Bassler

Publications and source records attributed to Kevin E Bassler.

8 recordsLinked to original sources

PubMed2006

Congestion-gradient driven transport on complex networks.

We present a study of transport on complex networks with routing based on local information. Particles hop from one node of the network to another according to a set of routing rules with different degrees of congestion awareness, ranging from random diffusion to rigid congestion-gradient driven flow. Each node can be either source or destination for particles and all nodes have the same routing capacity, which are features of ad hoc wireless networks. It is shown that the transport capacity increases when a small amount of congestion awareness is present in the routing rules, and that it then decreases as the routing rules become too rigid when the flow becomes strictly congestion-gradient driven. Therefore, an optimum value of the congestion awareness exists in the routing rules. It is also shown that, in the limit of a large number of nodes, networks using routing based on local information jam at any nonzero load. Finally, we study the correlation between congestion at node level and a betweenness centrality measure.

Journal Article↗

PubMed2006

Emergent criticality from coevolution in random Boolean networks.

The coevolution of network topology and dynamics is studied in an evolutionary Boolean network model that is a simple model of a gene regulatory network. We find that a critical state emerges spontaneously resulting from the interplay between topology and dynamics during the evolution. The final evolved state is shown to be independent of initial conditions. The network appears to be driven to a random Boolean network with uniform in-degree of 2 in the large-network limit. However, for biologically realized network sizes, significant finite-size effects are observed including a broad in-degree distribution and an average in-degree connections between 2 and 3. These results may be important for explaining the properties of gene regulatory networks.

Cell Physiological Phenomena↗

PubMed2006

Optimal transport on complex networks.

We present a heuristic algorithm for the optimization of transport on complex networks. Previously proposed network transport optimization algorithms aim at avoiding or reducing link overload. Our algorithm balances traffic on a network by minimizing the maximum node betweenness with as little path lengthening as possible, thus being useful in cases when networks are jamming due to node congestion. By using the resulting routing, a network can sustain significantly higher traffic without jamming than in the case of shortest path routing.

Journal Article↗

PubMed2006

Nonlinear evolution of surface morphology in InAs/AlAs superlattices via surface diffusion.

Continuum simulations of self-organized lateral compositional modulation growth in InAs/AlAs short-period superlattices on InP substrate are presented. The results of the simulations correspond quantitatively to the results of synchrotron x-ray diffraction experiments. The time evolution of the compositional modulation during epitaxial growth can be explained only including a nonlinear dependence of the elastic energy of the growing epitaxial layer on its thickness. From the fit of the experimental data to the growth simulations we have determined the parameters of this nonlinear dependence. It was found that the modulation amplitude does not depend on the values of the surface diffusion constants of particular elements.

Journal Article↗

PubMed2004

Evolution of developmental canalization in networks of competing boolean nodes.

Developmental canalization, which leads to a reduction in the variation of phenotype expression relative to the complexity of the genome, has long been thought to be an important property of evolving biological systems. We demonstrate that a highly canalized state develops in the process of self-organization recently discovered in N-K Boolean networks that evolve based on a competition between the nodes. The model provides a simplified description of the evolution of genetic regulatory networks in developmental systems. The mechanism responsible for the evolution is shown to be a balance of two dynamical effects which compete to bring the network to a nonrandom critical steady state. Unlike other proposed evolutionary mechanisms that select for canalization, this mechanism does so while maintaining the system's capacity for further evolution in the steady state.

Computer Simulation↗

PubMed2004

Network dynamics: jamming is limited in scale-free systems.

A large number of complex networks are scale-free--that is, they follow a power-law degree distribution. Here we propose that the emergence of many scale-free networks is tied to the efficiency of transport and flow processing across these structures. In particular, we show that for large networks on which flows are influenced or generated by gradients of a scalar distributed on the nodes, scale-free structures will ensure efficient processing, whereas structures that are not scale-free, such as random graphs, will become congested.

Journal Article↗

PubMed2004

Competition-driven network dynamics: emergence of a scale-free leadership structure and collective efficiency.

Using the minority game as a model for competition dynamics, we investigate the effects of interagent communications across a network on the global evolution of the game. Agent communication across this network leads to the formation of an influence network, which is dynamically coupled to the evolution of the game, and it is responsible for the information flow driving the agents' actions. We show that the influence network spontaneously develops hubs with a broad distribution of in-degrees, defining a scale-free robust leadership structure. Furthermore, in realistic parameter ranges, facilitated by information exchange on the network, agents can generate a high degree of cooperation making the collective almost maximally efficient.

Competitive Behavior↗

PubMed2002

Model for bone strength and osteoporotic fractures.

Inner porous regions play a critical role in the load bearing capability of large bones. We show that an extension of disordered elastic networks [Chung et al., Phys. Rev. B 54, 15 094 (1996)] exhibits analogs of several known mechanical features of bone. The "stress backbones" and histograms of stress distributions for healthy and weak networks are shown to be qualitatively different. A hereto untested relationship between bone density and bone strength is presented.

Aged↗