Internal Delay Research Articles

Predicting binaural responses from monaural responses in the gerbil medial superior olive.

Accurate sound source localization of low-frequency sounds in the horizontal plane depends critically on the comparison of arrival times at both ears. A specialized brainstem circuit containing the principal neurons of the medial superior olive (MSO) is dedicated to this comparison. MSO neurons are innervated by segregated inputs from both ears. The coincident arrival of excitatory inputs from both ears is thought to trigger action potentials, with differences in internal delays creating a unique sensitivity to interaural time differences (ITDs) for each cell. How the inputs from both ears are integrated by the MSO neurons is still debated. Using juxtacellular recordings, we tested to what extent MSO neurons from anesthetized Mongolian gerbils function as simple cross-correlators of their bilateral inputs. From the measured subthreshold responses to monaural wideband stimuli we predicted the rate-ITD functions obtained from the same MSO neuron, which have a damped oscillatory shape. The rate of the oscillations and the position of the peaks and troughs were accurately predicted. The amplitude ratio between dominant and secondary peaks of the rate-ITD function, captured in the width of its envelope, was not always exactly reproduced. This minor imperfection pointed to the methodological limitation of using a linear representation of the monaural inputs, which disregards any temporal sharpening occurring in the cochlear nucleus. The successful prediction of the major aspects of rate-ITD curves supports a simple scheme in which the ITD sensitivity of MSO neurons is realized by the coincidence detection of excitatory monaural inputs.

Adaptive stabilization and synchronization of non-diffusively coupled complex networks with nonidentical nodes of different dimensions

A class of non-diffusively coupled complex networks consisting of nodes of different dimensions is studied, in which the internal time delays are different from the coupling delays. Proper adaptive controllers are proposed for the stabilization and function matrix projective synchronization of such complex networks, respectively. The symmetric or diffusive conditions for the coupling matrices are not required. Finally, the results are applied to complex networks of chaotic oscillators showing the effectiveness of the proposed controllers.

Finite-time synchronization of complex dynamical networks with multi-links via intermittent controls

This paper considers finite-time synchronization of complex multi-links dynamical networks with or without internal time delays via intermittent controls. Two simple intermittent feedback controllers are designed to achieve finite-time synchronization between the drive and response system. Some novel and effective finite-time synchronization criteria are derived based on finite-time stability analysis techniques. By constructing suitable Lyapunov functions, we theoretically prove its correctness. Finally, two numerical simulation examples are given to show the effectiveness of proposed method in this paper.

A Mathematical Model for Cholesterol Biosynthesis under Nicotine Exposure

In this paper, a mathematical model is considered for analyzing the impact of nicotine exposure to cholesterol biosynthesis. The dynamical model is nonlinear. Its equilibrium points are computed and conditions are provided under which a unique locally stable positive equilibrium exists. Moreover, effect of internal time delays on local stability is also investigated.

Stability of some thermoelastic systems with internal time-varying delay

Stability of some thermoelastic systems with internal time-varying delay

RFID Tags Detectors Stability Analysis Under Delayed Schottky Diode’s Internal Elements in Time

In this article, we discuss the crucial subject of stability analysis of RFID tag detectors under Schottky diode’s internal time delay elements. The Schottky diode detector demodulates the signal and sends the data on to the digital circuit of the TAG; this is the so-called "wake up" signal. A simple RFID TAG receiver block diagram includes input antenna signal with series resistance, inductor (choke), Schottky diode, and output capacitor. Due to the Schottky parasitic delay, there is a stability issue in analyzing detector operation. We define τ1, τ2 as delays in time respectively for a Schottky equivalent circuit. We first consider those two delays in time that are not equal τ1≠τ2 then the other three cases τ1= τ & τ2=0, τ 2= τ & τ1=0, τ1= τ2= τ. The RFID receiver detector time delay equivalent circuit can be represent as delayed differential equations that depend on variable parameters and delays. The article illustrates certain observations, and analyzes local bifurcations of an appropriate arbitrary scalar delayed differential equation. All of that for optimization of an RFID receiver detector equivalent circuit parameters analysis to get the best performance.

Two-way time transfer via optical fiber providing subpicosecond precision and high temperature stability

We are reporting on analysis, design, construction, and key parameters of the device for a two-way time transfer via an optical fiber. The dominant source of errors in the two-way optical time transfer (TWOTT) via relatively short optical fibers is the temperature dependence of internal delays within the terminal units. We have performed an analysis of the influence of the internal delays and their temperature dependence on the TWOTT process considering two different configurations of the terminals with the feedback coupling in optical and electrical domains. The achieved results have been used for the optimal design of a TWOTT system implementing standard small form-factor pluggable optical transceivers. The operational tests of this new TWOTT system confirmed the precision of the time transfer on the subpicosecond level, the time transfer stability characterized by TDEV better than 60 fs for averaging intervals from 100 s to 10 000 s, and the temperature stability better than 100 fs K−1.

Towards higher stability of resonant absorption measurements in pulsed plasmas.

Possible ways to increase the reliability of time-resolved particle density measurements in pulsed gaseous discharges using resonant absorption spectroscopy are proposed. A special synchronization, called "dynamic source triggering," between a gated detector and two pulsed discharges, one representing the discharge of interest and another being used as a reference source, is developed. An internal digital delay generator in the intensified charge coupled device camera, used at the same time as a detector, is utilized for this purpose. According to the proposed scheme, the light pulses from the reference source follow the gates of detector, passing through the discharge of interest only when necessary. This allows for the utilization of short-pulse plasmas as reference sources, which is critical for time-resolved absorption analysis of strongly emitting pulsed discharges. In addition to dynamic source triggering, the reliability of absorption measurements can be further increased using simultaneous detection of spectra relevant for absorption method, which is also demonstrated in this work. The proposed methods are illustrated by the time-resolved measurements of the metal atom density in a high-power impulse magnetron sputtering (HiPIMS) discharge, using either a hollow cathode lamp or another HiPIMS discharge as a pulsed reference source.

The Role of Motion Extrapolation in Amphibian Prey Capture

Sensorimotor delays decouple behaviors from the events that drive them. The brain compensates for these delays with predictive mechanisms, but the efficacy and timescale over which these mechanisms operate remain poorly understood. Here, we assess how prediction is used to compensate for prey movement that occurs during visuomotor processing. We obtained high-speed video records of freely moving, tongue-projecting salamanders catching walking prey, emulating natural foraging conditions. We found that tongue projections were preceded by a rapid head turn lasting ∼ 130 ms. This motor lag, combined with the ∼ 100 ms phototransduction delay at photopic light levels, gave a ∼ 230 ms visuomotor response delay during which prey typically moved approximately one body length. Tongue projections, however, did not significantly lag prey position but were highly accurate instead. Angular errors in tongue projection accuracy were consistent with a linear extrapolation model that predicted prey position at the time of tongue contact using the average prey motion during a ∼ 175 ms period one visual latency before the head movement. The model explained successful strikes where the tongue hit the fly, and unsuccessful strikes where the fly turned and the tongue hit a phantom location consistent with the fly's earlier trajectory. The model parameters, obtained from the data, agree with the temporal integration and latency of retinal responses proposed to contribute to motion extrapolation. These results show that the salamander predicts future prey position and that prediction significantly improves prey capture success over a broad range of prey speeds and light levels. Neural processing delays cause actions to lag behind the events that elicit them. To cope with these delays, the brain predicts what will happen in the future. While neural circuits in the retina and beyond have been suggested to participate in such predictions, few behaviors have been explored sufficiently to constrain circuit function. Here we show that salamanders aim their tongues by using extrapolation to estimate future prey position, thereby compensating for internal delays from both visual and motor processing. Predictions made just before a prey turn resulted in the tongue being projected to a position consistent with the prey's pre-turn trajectory. These results define the computations and operating regimen for neural circuits that predict target motion.

Impact of Delays for Electric Vehicles With Direct Yaw Moment Control

This paper investigates the impact of time delay factors on the lateral motion of electric vehicles with direct yaw moment control (DYC). The existence of internal time delay factors is inescapable in electric vehicle (EV) systems, which might affect the effectiveness of DYC. Computer simulation shows that DYC works well at small time delays, while significant oscillation or even loss of stability occurs when the delays are large enough. A frequency-domain method is used to determine the stability limit of the time-delayed system.

Measured Ionospheric Delay Corrections for Code-based GPS Time Transfer

In Global Positioning System (GPS) time transfer measurements, all of the delays in receiving GPS timing signals, including the ionospheric delay in the signal path and the internal delay of a GPS ...

Behavior and modeling of two-dimensional precedence effect in head-unrestrained cats.

The precedence effect (PE) is an auditory illusion that occurs when listeners localize nearly coincident and similar sounds from different spatial locations, such as a direct sound and its echo. It has mostly been studied in humans and animals with immobile heads in the horizontal plane; speaker pairs were often symmetrically located in the frontal hemifield. The present study examined the PE in head-unrestrained cats for a variety of paired-sound conditions along the horizontal, vertical, and diagonal axes. Cats were trained with operant conditioning to direct their gaze to the perceived sound location. Stereotypical PE-like behaviors were observed for speaker pairs placed in azimuth or diagonally in the frontal hemifield as the interstimulus delay was varied. For speaker pairs in the median sagittal plane, no clear PE-like behavior occurred. Interestingly, when speakers were placed diagonally in front of the cat, certain PE-like behavior emerged along the vertical dimension. However, PE-like behavior was not observed when both speakers were located in the left hemifield. A Hodgkin-Huxley model was used to simulate responses of neurons in the medial superior olive (MSO) to sound pairs in azimuth. The novel simulation incorporated a low-threshold potassium current and frequency mismatches to generate internal delays. The model exhibited distinct PE-like behavior, such as summing localization and localization dominance. The simulation indicated that certain encoding of the PE could have occurred before information reaches the inferior colliculus, and MSO neurons with binaural inputs having mismatched characteristic frequencies may play an important role.

High-performance reconfigurable coincidence counting unit based on a field programmable gate array.

We present a high-performance reconfigurable coincidence counting unit (CCU) using a low-end field programmable gate array (FPGA) and peripheral circuits. Because of the flexibility guaranteed by the FPGA program, we can easily change system parameters, such as internal input delays, coincidence configurations, and the coincidence time window. In spite of a low-cost implementation, the proposed CCU architecture outperforms previous ones in many aspects: it has 8 logic inputs and 4 coincidence outputs that can measure up to eight-fold coincidences. The minimum coincidence time window and the maximum input frequency are 0.47ns and 163MHz, respectively. The CCU will be useful in various experimental research areas, including the field of quantum optics and quantum information.

Finite-time synchronization of coupled networks with one single time-varying delay coupling

This paper studies finite-time synchronization of hybrid coupled networks. There is only one transmittal delay in the delayed coupling. The fact is that in the signal transmission process, the time delay affects only the variable that is being transmitted from one system to another, so assume that there is only one single time-varying delay coupling is more consistent with the reality. At the same time, the internal delay and coupling delay are time-varying and different. Based on the Lyapunov stability theory, a feedback controller is designed for achieving synchronization between two coupled networks with time-varying delays in finite time. Finally, simulation examples are given to illustrate the theoretical analysis.

Synchronization analysis of hybrid-coupled delayed dynamical networks with impulsive effects: A unified synchronization criterion

This paper addresses the problem of globally exponential synchronization for a class of general hybrid-coupled impulsive delayed dynamical networks with both internal delay and coupling delay. A more general delayed coupling term involving the transmission delay and self-feedback delay is considered. Additionally, two types of impulses occurred in the states of nodes are taken into account: (i) synchronizing impulses defined as they can enhance the synchronization of dynamical networks; and (ii) desynchronizing impulses meaning that they can suppress the synchronization of dynamical networks. By establishing an improved impulsive differential inequality derived based on the average impulsive interval approach, a simpler and less conservative unified globally exponential synchronization criterion is obtained, which is simultaneously effective for synchronizing and desynchronizing impulses. It is shown that the obtained criterion is closely related with impulse strengths, average impulsive interval, and topology structure of the networks. Finally, numerical examples including a typical nearest-neighbor unidirectional coupled network and a scale-free network are given to demonstrate the applicability and efficiency of the theoretical results.

In vivo coincidence detection in mammalian sound localization generates phase delays.

Sound localization critically depends on detection of differences in arrival time of sounds at the two ears (acoustic delay). The fundamental mechanisms are debated, but all proposals include a process of coincidence detection and a separate source of internal delay which offsets the acoustic delay and determines neural tuning. We obtained in vivo patch clamp recordings of binaural neurons in the Mongolian gerbil, combined with pharmacological manipulations, to directly compare neuronal input to output and to separate excitation from inhibition. The results cannot be accounted for by existing models and reveal that coincidence detection is not an instantaneous process but is shaped by the interaction of intrinsic conductances with preceding synaptic activity. This interaction generates an internal delay as an intrinsic part of the process of coincidence detection. The multiplication and time-shifting stages thought to extract synchronous activity in many brain areas can thus be combined in a single operation.

The Speed of Visual Attention and Motor-Response Decisions in Adult Attention-Deficit/Hyperactivity Disorder

BackgroundAdults with attention-deficit/hyperactivity disorder (ADHD) exhibit slowed reaction times (RTs) in various attention tasks. The exact origins of this slowing, however, have not been established. Potential candidates are early sensory processes mediating the deployment of focal attention, stimulus response translation processes deciding upon the appropriate motor response, and motor processes generating the response. MethodsWe combined mental chronometry (RT) measures of adult ADHD (n = 15) and healthy control (n = 15) participants with their lateralized event-related potentials during the performance of a visual search task to differentiate potential sources of slowing at separable levels of processing: the posterior contralateral negativity (PCN) was used to index focal-attentional selection times, while the lateralized readiness potentials synchronized to stimulus and response events were used to index the times taken for response selection and production, respectively. To assess the clinical relevance of event-related potentials, a correlation analysis between neural measures and subjective current and retrospective ADHD symptom ratings was performed. ResultsADHD patients exhibited slower RTs than control participants, which were accompanied by prolonged PCN and lateralized readiness potentials synchronized to stimulus, but not lateralized readiness potentials synchronized to response events, latencies. Moreover, the PCN timing was positively correlated with ADHD symptom ratings. ConclusionsThe behavioral RT slowing of adult ADHD patients was based on a summation of internal processing delays arising at perceptual and response selection stages; motor response production, by contrast, was not impaired. The correlation between PCN times and ADHD symptom ratings suggests that this brain signal may serve as a potential candidate for a neurocognitive endophenotype of ADHD.

Asymptotic behavior of weakly dissipative Timoshenko system with internal constant delay feedbacks

In this paper, we consider a one-dimensional Timoshenko system with a linear frictional damping and a constant delay acting on the displacement equation. Under appropriate assumptions on the weight of the delay and the wave speeds, we establish the well posedness and asymptotic stability results of the system. Our stability results show that the dissipation through the frictional damping is strong enough to uniformly stabilize the system even in the presence of delay.

On the Stability and Equilibrium Points of MultistagedSI(n)REpidemic Models

This paper relies on the concept of next generation matrix defined ad hoc for a new proposed extended SEIR model referred to asSI(n)R-model to study its stability. The model includesnsuccessive stages of infectious subpopulations, each one acting at the exposed subpopulation of the next infectious stage in a cascade global disposal where each infectious population acts as the exposed subpopulation of the next infectious stage. The model also has internal delays which characterize the time intervals of the coupling of the susceptible dynamics with the infectious populations of the various cascade infectious stages. Since the susceptible subpopulation is common, and then unique, to all the infectious stages, its coupled dynamic action on each of those stages is modeled with an increasing delay as the infectious stage index increases from 1 ton. The physical interpretation of the model is that the dynamics of the disease exhibits different stages in which the infectivity and the mortality rates vary as the individual numbers go through the process of recovery, each stage with a characteristic average time.

Breaking down the silos to decrease internal diversions and patient flow delays.

Hospitals strive to admit patients to the units where caregiver competencies align with the patient's condition. When the hospital's census peaks, internal diversions and the associated risks increase, which are intensified when silos exist, as segregated care negatively impacts collaboration and patient safety. In this study, a 600+-bed academic, tertiary care specialty hospital experienced an increase in internal diversions. Within the neuroscience service line, emergent neuroscience transfers from outside hospitals had been declined or internally diverted because of capacity limitations. Formalized processes for improving collaboration between health care providers related to capacity issues were required to decrease internal diversions and improve patient flow and patient safety. A pilot project was conducted on neuroscience units during a process improvement initiative. A hospital-wide internal diversion plan was developed, identifying primary and secondary placement options for all patients requiring hospitalization to support patient flow and patient safety. Forecasting tools were developed to provide units' leadership with current information on expected admissions. Daily capacity huddles were instituted to increase collaboration between patient care units. The interventions trialed during the pilot decreased internal diversions and improved patient flow. The improved collaboration resulted in an 80% decrease in declinations of emergent intensive care unit transfers from outside hospitals due to capacity limitations and a 50% decrease in the number of these patients being internally diverted to alternate intensive care units. The interventions implemented minimized internal diversions and improved patient flow. The transparency of the patient placement process led to an increased collaboration between all participants.