6,636 research outputs found
Chaos and Fractals around Black Holes
Fractal basin boundaries provide an important means of characterizing chaotic
systems. We apply these ideas to general relativity, where other properties
such as Lyapunov exponents are difficult to define in an observer independent
manner. Here we discuss the difficulties in describing chaotic systems in
general relativity and investigate the motion of particles in two- and
three-black-hole spacetimes. We show that the dynamics is chaotic by exhibiting
the basins of attraction of the black holes which have fractal boundaries.
Overcoming problems of principle as well as numerical difficulties, we evaluate
Lyapunov exponents numerically and find that some trajectories have a positive
exponent.Comment: To appear in "Fractals" March issue (World Scientific), 20 figures
available by request, also available from SLAC's gr-qc postscript archiv
Model of host-pathogen Interaction dynamics links In vivo optical imaging and immune responses
Tracking disease progression in vivo is essential for the development of treatments against bacterial infection. Optical imaging has become a central tool for in vivo tracking of bacterial population development and therapeutic response. For a precise understanding of in vivo imaging results in terms of disease mechanisms derived from detailed postmortem observations, however, a link between the two is needed. Here, we develop a model that provides that link for the investigation of Citrobacter rodentium infection, a mouse model for enteropathogenic Escherichia coli (EPEC). We connect in vivo disease progression of C57BL/6 mice infected with bioluminescent bacteria, imaged using optical tomography and X-ray computed tomography, to postmortem measurements of colonic immune cell infiltration. We use the model to explore changes to both the host immune response and the bacteria and to evaluate the response to antibiotic treatment. The developed model serves as a novel tool for the identification and development of new therapeutic interventions
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