46 research outputs found
Propagation failure of traveling waves in a discrete bistable medium
Propagation failure (pinning) of traveling waves is studied in a discrete
scalar reaction-diffusion equation with a piecewise linear, bistable reaction
function. The critical points of the pinning transition, and the wavefront
profile at the onset of propagation are calculated exactly. The scaling of the
wave speed near the transition, and the leading corrections to the front shape
are also determined. We find that the speed vanishes logarithmically close to
the critical point, thus the model belongs to a different universality class
than the standard Nagumo model, defined with a smooth, polynomial reaction
function.Comment: 8 pages, 6 eps figures, to appear in Physica
Rapid Phenotype-Driven Gene Sequencing with the NeoSeq Panel: A Diagnostic Tool for Critically Ill Newborns with Suspected Genetic Disease
New genomic sequencing techniques have shown considerable promise in the field of neonatology, increasing the diagnostic rate and reducing time to diagnosis. However, several obstacles have hindered the incorporation of this technology into routine clinical practice. We prospectively evaluated the diagnostic rate and diagnostic turnaround time achieved in newborns with suspected genetic diseases using a rapid phenotype-driven gene panel (NeoSeq) containing 1870 genes implicated in congenital malformations and neurological and metabolic disorders of early onset (<2 months of age). Of the 33 newborns recruited, a genomic diagnosis was established for 13 (39.4%) patients (median diagnostic turnaround time, 7.5 days), resulting in clinical management changes in 10 (76.9%) patients. An analysis of 12 previous prospective massive sequencing studies (whole genome (WGS), whole exome (WES), and clinical exome (CES) sequencing) in newborns admitted to neonatal intensive care units (NICUs) with suspected genetic disorders revealed a comparable median diagnostic rate (37.2%), but a higher median diagnostic turnaround time (22.3 days) than that obtained with NeoSeq. Our phenotype-driven gene panel, which is specific for genetic diseases in critically ill newborns is an affordable alternative to WGS and WES that offers comparable diagnostic efficacy, supporting its implementation as a first-tier genetic test in NICUs
Doppler Effect of Nonlinear Waves and Superspirals in Oscillatory Media
Nonlinear waves emitted from a moving source are studied. A meandering spiral
in a reaction-diffusion medium provides an example, where waves originate from
a source exhibiting a back-and-forth movement in radial direction. The periodic
motion of the source induces a Doppler effect that causes a modulation in
wavelength and amplitude of the waves (``superspiral''). Using the complex
Ginzburg-Landau equation, we show that waves subject to a convective Eckhaus
instability can exhibit monotonous growth or decay as well as saturation of
these modulations away from the source depending on the perturbation frequency.
Our findings allow a consistent interpretation of recent experimental
observations concerning superspirals and their decay to spatio-temporal chaos.Comment: 4 pages, 4 figure
Exponential synchronization of complex networks with Markovian jump and mixed delays
This is the post print version of the article. The official published version can be obtained from the link - Copyright 2008 Elsevier LtdIn this Letter, we investigate the exponential synchronization problem for an array of N linearly coupled complex networks with Markovian jump and mixed time-delays. The complex network consists of m modes and the network switches from one mode to another according to a Markovian chain with known transition probability. The mixed time-delays are composed of discrete and distributed delays, both of which are mode-dependent. The nonlinearities imbedded with the complex networks are assumed to satisfy the sector condition that is more general than the commonly used Lipschitz condition. By making use of the Kronecker product and the stochastic analysis tool, we propose a novel Lyapunov–Krasovskii functional suitable for handling distributed delays and then show that the addressed synchronization problem is solvable if a set of linear matrix inequalities (LMIs) are feasible. Therefore, a unified LMI approach is developed to establish sufficient conditions for the coupled complex network to be globally exponentially synchronized in the mean square. Note that the LMIs can be easily solved by using the Matlab LMI toolbox and no tuning of parameters is required. A simulation example is provided to demonstrate the usefulness of the main results obtained.This work was supported in part by the Biotechnology and Biological Sciences Research Council (BBSRC) of the UK under Grants BB/C506264/1 and 100/EGM17735, the Engineering and Physical Sciences Research Council (EPSRC) of the UK under Grants GR/S27658/01 and EP/C524586/1, an International Joint Project sponsored by the Royal Society of the UK, the Natural Science Foundation of Jiangsu Province of China under Grant BK2007075, the National Natural Science Foundation of China under Grant 60774073, and the Alexander von Humboldt Foundation of Germany
Time scales and species coexistence in chaotic flows
Empirical observations in marine ecosystems have suggested a balance of
biological and advection time scales as a possible explanation of species
coexistence. To characterise this scenario, we measure the time to fixation in
neutrally evolving populations in chaotic flows. Contrary to intuition the
variation of time scales does not interpolate straightforwardly between the
no-flow and well-mixed limits; instead we find that fixation is the slowest at
intermediate Damk\"ohler numbers, indicating long-lasting coexistence of
species. Our analysis shows that this slowdown is due to spatial organisation
on an increasingly modularised network. We also find that diffusion can either
slow down or speed up fixation, depending on the relative time scales of flow
and evolution.Comment: 5 pages, 4 figure
Particle tracking of inertial and Lagrangian particles in isotropic turbulence flows
The motion of contracting and expanding bubbles in an incompressible chaotic flow is analyzed in terms of the Finite-Time Lyapunov Exponents. The viscous forces acting on the bubble surface depend not only on the relative acceleration but also on the time-dependence of the bubble volume which is modeled by the Rayleigh-Plesset equation. The effect of bubbles coalescence on the coherent structmes that develop in the flow is studied using a simplified bubble merger model. Contraction and expansion of the bubbles is favored in the vicinity of the coherent structures. Mixing patterns were found to depend heavily on merging and on the time-dependent volume of the bubbles
Pattern formation in reaction-diffusion systems under forcing
info:eu-repo/semantics/publishe