Dynamic Markers for Chaotic Motion in C. elegans.

We describe the locomotion of Caenorhabditis elegans (C. elegans) using nonlinear dynamics. C.

Pacemaker-Based Cardiac Neuromodulation Therapy in Patients With Hypertension: A Pilot Study.

Background In prior unblinded studies, cardiac neuromodulation therapy (CNT) employing a sequence of variably timed short and longer atrioventricular intervals yielded sustained reductions of systolic blood pressure (SBP) in patients with hypertension. The effects of CNT on SBP were investigated in this double-blind randomized pilot study. Methods and Results Eligible patients had daytime ambulatory SBP (aSBP) ≥130 mm Hg and office SBP ≥140 mm Hg despite taking ≥1 antihypertensive medication, and an indication for a dual-chamber pacemaker.

Fourier-Based Diffraction Analysis of Live Caenorhabditis elegans.

This manuscript describes how to classify nematodes using temporal far-field diffraction signatures. A single C. elegans is suspended in a water column inside an optical cuvette.

Fishing Quotas, Induced Allee Effect, and Fluctuation-Driven Extinction.

We explore the potential of modifications to standard fishery models (for example Gordon-Schafer-Munro) to help understand events such as the collapse of the North Atlantic cod fishery. In particular we find that quota-driven and similar harvesting strategies induce an effective strong Allee effect (collapse if the population falls below a critical level). In the presence of environmental noise, fish population dynamics is similar to a random walk with (non-linear) drift.

Oregonator Scaling Motivated by the Showalter-Noyes Limit.

The Belousov-Zhabotinsky (BZ) reaction is the prototype oscillatory chemical system. We investigate here a new scaling of the Oregonator model of BZ chemical kinetics and use this scaling to elucidate fundamental properties of BZ dynamics. In particular, the Showalter-Noyes criterion for oscillation, that the product [BrO][H] exceeds a critical value, arises naturally as a subcritical Hopf bifurcation in this setting, as does the reduction to a two-variable model.

Weaning of extracorporeal membrane oxygenation using continuous hemodynamic transesophageal echocardiography.

Background: Venoarterial extracorporeal membrane oxygenation (VA ECMO) has been used for profound cardiogenic shock to bridge to decision, ventricular assist device(s) (VADs), or transplant. To assess ventricular function and volume status along with hemodynamics during ECMO weaning, we developed a standardized weaning protocol, guided by a miniaturized transesophageal echocardiography probe designed for continuous hemodynamic monitoring (hemodynamic transesophageal echocardiography [hTEE]). We reviewed our experience with this weaning protocol with hTEE guidance to assess if we could predict patient outcomes.

Dynamics of human atrial cell models: restitution, memory, and intracellular calcium dynamics in single cells.

Mathematical models of cardiac cells have become important tools for investigating the electrophysiological properties and behavior of the heart. As the number of published models increases, it becomes more difficult to choose a model appropriate for the conditions to be studied, especially when multiple models describing the species and region of the heart of interest are available. In this paper, we will review and compare two detailed ionic models of human atrial myocytes, the Nygren et al.

Bromide control, bifurcation and activation in the Belousov-Zhabotinsky reaction.

The unstirred, ferroin (Fe(phen)3(2+)) catalyzed Belousov-Zhabotinsky (BZ) reaction is the prototype oscillatory chemical system. Reaction media with added Br(-) appear red (reduced, low [Fe(phen)3(3+)]) during an induction period of several minutes, followed by the "spontaneous" formation of "pacemaker" sites, which oscillate between a blue, oxidized state (high [Fe(phen)3(3+)]) and the red, reduced state and generate target patterns of concentric, outwardly moving waves of oxidation (blue). Auto-oscillatory behavior is also seen in the Oregonator model of Field, Koros and Noyes (FKN), a robust, reduced model that captures qualitative BZ kinetics in the auto-oscillatory regime.

Controlled excitations of the Belousov-Zhabotinsky reaction: Experimental procedures.

The purpose of this research was to explore the unstirred, ferroin-catalyzed Belousov-Zhabotinsky (BZ) reaction as an experimental model for the response of excitable media to small perturbations (slightly larger than the threshold for excitations). Following Showalter et al. (Showalter, K.

Oxidation state of BZ reaction mixtures.

The unstirred, ferroin (Fe(phen)(3)2+)-catalyzed Belousov-Zhabotinsky (BZ) reaction1-4 is the prototype oscillatory chemical system. After an induction period of several minutes, one sees "spontaneous" formation of "pacemaker" sites, which oscillate between a blue, oxidized state (high [Fe(phen)3(3+)]) and a red, reduced state (low [Fe(phen)(3)3+]). The reaction medium appears red (reduced) during the induction phase, and the pacemaker sites generate target patterns of concentric, outwardly moving waves of oxidation (blue).

The relationship of fall school opening and emergency department asthma visits in a large metropolitan area.

Background: Asthma morbidity is seasonal, with the fewest exacerbations occurring in summer and the most exacerbations in early fall.

Objective: To determine if the fall increase in pediatric asthma emergency department (ED) visits is related to the school year start.

Design: Time-series study of daily asthma ED visits taken from an administrative claims database for the years 1991 to 2002.

Spatiotemporal clustering and temporal order in the excitable BZ reaction.

The prototype experimental example of "spontaneous" pattern formation in an unstirred chemical medium is the oscillatory Belousov-Zhabotinsky (BZ) reaction: target patterns of outward-moving concentric rings are readily observed when the reaction is run in a thin layer in a Petri dish. In many experimental runs, new target centers appeared to form closer to pre-existing target centers than expected in a randomized model. Here we describe a simple direct test for the presence of temporal order in the spatiotemporal dynamics of target nucleation, and apply this test to detect significant temporal order in target formation in the ferroin-catalyzed BZ reaction.

Age-related seasonal patterns of emergency department visits for acute asthma in an urban environment.

Study Objective: Asthma morbidity is greater in younger patients. The reasons are not fully understood, although identifying demographic patterns of seasonality may help determine causes and potential prevention. The objective of this study is to determine the relationship between age and seasonal asthma periodicity in patients presenting to the emergency department (ED).

Multiple mechanisms of spiral wave breakup in a model of cardiac electrical activity.

It has become widely accepted that the most dangerous cardiac arrhythmias are due to reentrant waves, i.e., electrical wave(s) that recirculate repeatedly throughout the tissue at a higher frequency than the waves produced by the heart's natural pacemaker (sinoatrial node).

Real-time computer simulations of excitable media: JAVA as a scientific language and as a wrapper for C and FORTRAN programs.

We describe a useful setting for interactive, real-time study of mathematical models of cardiac electrical activity, using implicit and explicit integration schemes implemented in JAVA. These programs are intended as a teaching aid for the study and understanding of general excitable media. Particularly for cardiac cell models and the ionic currents underlying their basic electrical dynamics.