Excitable Dynamics in the Presence of Time Delay

The spiking properties of a subcritical Hopf oscillator with a time delayed nonlinear feedback is investigated. Finite time delay is found to significantly affect both the statistics and the fine structure of the spiking behavior. These dynamical changes are explained in terms of the fundamental modifications occurring in the bifurcation scenario of the system. Our mathematical model can find useful applications in understanding the dynamical behaviour of various real life excitable systems where propagation delay effects are ubiquitous.Comment: 10 pages including 7 figure

Resonance between Noise and Delay

We propose here a stochastic binary element whose transition rate depends on its state at a fixed interval in the past. With this delayed stochastic transition this is one of the simplest dynamical models under the influence of ``noise'' and ``delay''. We demonstrate numerically and analytically that we can observe resonant phenomena between the oscillatory behavior due to noise and that due to delay.Comment: 4 pages, 5 figures, submitted to Phys.Rev.Lett Expanded and Added Reference

Development of an empathy and clarity rating scale to measure the effect of medical improv on end-of-first-year OCSE performance: a pilot study

Patients want empathetic physicians who listen and understand. How do you teach and measure empathy? Medical educators, including those inspired by Alan Alda, have turned to theater to teach skills in empathetic communication. Improvisation-informedcurriculum (medical improv) draws upon foundational actors training: deep listening, emotional understanding, connections, authenticity. Arating scale to measure the impact of medical improv on empathetic and clear communication does not exist. Objective: To develop aframework and instrument, the Empathy and Clarity Rating Scale (ECRS), for measuring communication elements used by actors and physicians, and pilot ECRS to test effectiveness of medical improv on first-yearstudents' communication skills. Design: Four medical schools collaborated. USMLE Step 2 Communication and Interpersonal Skills (CIS) domains were used as framework for discussion among three focus groups, each with clinicians, actors, communication experts, and community members with patient experience. Audiotaped discussions were transcribed; open coding procedures located emerging themes. The initial coding scheme was compared with the Consultation and Relational Empathy (CARE) measure. ECRS content was aligned with CARE, CIS and focus group themes. Modified nominal processes were conducted to finalize the scale. We implemented procedures to establish content validity and interrater reliability. Final ECRS was used to study student performance across three levels of experience with medical improv. Results: The final ECRS was comprised of seven five-pointscale items. Narrative comments precede behaviorally anchored ratings: 5=desired, 1=ineffective, 2-4=developing based upon adjustment needed. Rater agreement across all items was 84%. There was asmall correlation between the ECRS and another measure interviewing (r=0.262, p=0.003). Students with advanced medical improv training outperformed those without (F=3.51, p=.042). Conclusion: Acommunication scale enlightened by experiences of actors, clinicians, scholars and patients has been developed. The ECRS has potential to detect the impact of medical improv on development of empathetic and clear communication

Stochastic Resonance in Nonpotential Systems

We propose a method to analytically show the possibility for the appearance of a maximum in the signal-to-noise ratio in nonpotential systems. We apply our results to the FitzHugh-Nagumo model under a periodic external forcing, showing that the model exhibits stochastic resonance. The procedure that we follow is based on the reduction to a one-dimensional dynamics in the adiabatic limit, and in the topology of the phase space of the systems under study. Its application to other nonpotential systems is also discussed.Comment: Submitted to Phys. Rev.

Statistical-Mechanical Measure of Stochastic Spiking Coherence in A Population of Inhibitory Subthreshold Neurons

By varying the noise intensity, we study stochastic spiking coherence (i.e., collective coherence between noise-induced neural spikings) in an inhibitory population of subthreshold neurons (which cannot fire spontaneously without noise). This stochastic spiking coherence may be well visualized in the raster plot of neural spikes. For a coherent case, partially-occupied "stripes" (composed of spikes and indicating collective coherence) are formed in the raster plot. This partial occupation occurs due to "stochastic spike skipping" which is well shown in the multi-peaked interspike interval histogram. The main purpose of our work is to quantitatively measure the degree of stochastic spiking coherence seen in the raster plot. We introduce a new spike-based coherence measure $M_s$ by considering the occupation pattern and the pacing pattern of spikes in the stripes. In particular, the pacing degree between spikes is determined in a statistical-mechanical way by quantifying the average contribution of (microscopic) individual spikes to the (macroscopic) ensemble-averaged global potential. This "statistical-mechanical" measure $M_s$ is in contrast to the conventional measures such as the "thermodynamic" order parameter (which concerns the time-averaged fluctuations of the macroscopic global potential), the "microscopic" correlation-based measure (based on the cross-correlation between the microscopic individual potentials), and the measures of precise spike timing (based on the peri-stimulus time histogram). In terms of $M_s$, we quantitatively characterize the stochastic spiking coherence, and find that $M_s$ reflects the degree of collective spiking coherence seen in the raster plot very well. Hence, the "statistical-mechanical" spike-based measure $M_s$ may be used usefully to quantify the degree of stochastic spiking coherence in a statistical-mechanical way.Comment: 16 pages, 5 figures, to appear in the J. Comput. Neurosc

A Tool to Recover Scalar Time-Delay Systems from Experimental Time Series

We propose a method that is able to analyze chaotic time series, gained from exp erimental data. The method allows to identify scalar time-delay systems. If the dynamics of the system under investigation is governed by a scalar time-delay differential equation of the form $dy(t)/dt = h(y(t),y(t-\tau_0))$, the delay time $\tau_0$ and the functi on $h$ can be recovered. There are no restrictions to the dimensionality of the chaotic attractor. The method turns out to be insensitive to noise. We successfully apply the method to various time series taken from a computer experiment and two different electronic oscillators

Stepping Stones: A Leadership Development Program to Inspire and Promote Reflection Among Women Faculty and Staff

Women frequently benefit from focused faculty development opportunities not because they need to be “fixed,” but rather it is a means to demonstrate that success, even in chilly environments, is possible. The Stepping Stones program uses a unique design to provide participants with inspiration, time for reflection, and strategies for how to navigate one's career, through hearing about the journeys of successful women. In this article, we describe the program and evaluation results. Post‐event and longitudinal follow‐up surveys indicate that the program and its unique narrative format help to debunk the superwoman myth and leave participants with a sense of optimism about their future careers

Stimulus - response curves of a neuronal model for noisy subthreshold oscillations and related spike generation

We investigate the stimulus-dependent tuning properties of a noisy ionic conductance model for intrinsic subthreshold oscillations in membrane potential and associated spike generation. On depolarization by an applied current, the model exhibits subthreshold oscillatory activity with occasional spike generation when oscillations reach the spike threshold. We consider how the amount of applied current, the noise intensity, variation of maximum conductance values and scaling to different temperature ranges alter the responses of the model with respect to voltage traces, interspike intervals and their statistics and the mean spike frequency curves. We demonstrate that subthreshold oscillatory neurons in the presence of noise can sensitively and also selectively be tuned by stimulus-dependent variation of model parameters.Comment: 19 pages, 7 figure

Characteristics of radiation absorption in metallic particles

Thermal radiation absorption in metallic particles is an important phenomenon in many Introduction Laser cladding is a very promising surface modification technique that can dramatically increase surface hardness and surface resistance to wear and corrosion Radiation-particle interactions often involve strong refraction and diffraction phenomena at the particle surface, which can enhance radiation absorption