scholarly journals Robust spike timing in an excitable cell with delayed feedback

2021 ◽  
Vol 18 (177) ◽  
Author(s):  
Kyle C. A. Wedgwood ◽  
Piotr Słowiński ◽  
James Manson ◽  
Krasimira Tsaneva-Atanasova ◽  
Bernd Krauskopf
Keyword(s):  
Mathematical Model ◽  
Critical Role ◽  
Experimental System ◽  
Propagation Speed ◽  
Delayed Feedback ◽  
Spike Timing ◽  
General Nature ◽  
Biological Cell ◽  
Electrical Impulses ◽  
Finite Propagation Speed

The initiation and regeneration of pulsatile activity is a ubiquitous feature observed in excitable systems with delayed feedback. Here, we demonstrate this phenomenon in a real biological cell. We establish a critical role of the delay resulting from the finite propagation speed of electrical impulses in the emergence of persistent multiple-spike patterns. We predict the coexistence of a number of such patterns in a mathematical model and use a biological cell subject to dynamic clamp to confirm our predictions in a living mammalian system. Given the general nature of our mathematical model and experimental system, we believe that our results capture key hallmarks of physiological excitability that are fundamental to information processing.

scholarly journals Time-Delay Identification Using Multiscale Ordinal Quantifiers

Entropy ◽  
2021 ◽  
Vol 23 (8) ◽  
pp. 969
Author(s):  
Miguel C. Soriano ◽  
Luciano Zunino
Keyword(s):  
Time Series ◽  
Time Delay ◽  
Real World ◽  
Propagation Speed ◽  
Real World Data ◽  
External Observer ◽  
The North ◽  
Weather Phenomenon ◽  
The North Atlantic Oscillation ◽  
Finite Propagation Speed

Time-delayed interactions naturally appear in a multitude of real-world systems due to the finite propagation speed of physical quantities. Often, the time scales of the interactions are unknown to an external observer and need to be inferred from time series of observed data. We explore, in this work, the properties of several ordinal-based quantifiers for the identification of time-delays from time series. To that end, we generate artificial time series of stochastic and deterministic time-delay models. We find that the presence of a nonlinearity in the generating model has consequences for the distribution of ordinal patterns and, consequently, on the delay-identification qualities of the quantifiers. Here, we put forward a novel ordinal-based quantifier that is particularly sensitive to nonlinearities in the generating model and compare it with previously-defined quantifiers. We conclude from our analysis on artificially generated data that the proper identification of the presence of a time-delay and its precise value from time series benefits from the complementary use of ordinal-based quantifiers and the standard autocorrelation function. We further validate these tools with a practical example on real-world data originating from the North Atlantic Oscillation weather phenomenon.

Resource Similarity, Market Commonality, and Spatial Distribution of Hotel Competitive Sets

2021 ◽  
pp. 109634802098857
Author(s):  
Zvi Schwartz ◽  
Timothy Webb
Keyword(s):  
Mathematical Model ◽  
Spatial Distribution ◽  
Performance Evaluation ◽  
Critical Role ◽  
Principal Agent ◽  
Large Dataset ◽  
Principal Agent Theory ◽  
Agent Theory ◽  
Performance And Evaluation

Index scores and competitive sets (compsets) play a critical role in the performance and evaluation of hotels. The reliance on these metrics has drawn skepticism in recent years as competitive sets may be opportunistically chosen, creating bias in performance evaluation. Drawing from the principal–agent theory and the theory of incentives, we explore whether the distance of the competitors chosen for a hotel’s compset influences revenue per available room (RevPAR) index scores. Based on the concepts of resource similarity and market commonality, we develop a novel mathematical model through which we empirically analyze a large dataset of 10,000 compsets. We find evidence that competitor distance influences index performance and that this relationship is bidirectional. Results show that hotels that outperform the competition may use distance to inflate RevPAR indices, while those that underperform may use distance to further reduce scores. These conflicting results may be reflected from the reverse motivations of the stakeholders.

An Experimental Study of Tendon Vibration Control System for Flexible Space Structures

1991 ◽  
Author(s):  
Yoshisada Murotsu ◽  
Hiroshi Okubo ◽  
Kei Senda
Keyword(s):  
Mathematical Model ◽  
Control System ◽  
Vibration Control ◽  
Transfer Functions ◽  
Mimo Systems ◽  
Experimental System ◽  
Space Structures ◽  
Flexible Beam ◽  
Tendon Vibration ◽  
Large Space

Abstract The idea of a tendon vibration control system for a beam-like flexible space structure has been proposed. To verify the feasibility of the concept, an experimental tendon control system has been constructed for the vibration control of a flexible beam simulating Large Space Structures (LSS). This paper discusses modeling, identification, actuator disposition, and controller design for the experimental system. First, a mathematical model of the whole system of the beam and tendon actuator is developed through a finite element method (FEM). Second, to obtain an accurate mathematical model for designing a controller, unknown characteristic parameters are estimated by using an output error method. The validity of the proposed identification scheme is demonstrated by good agreement between the transfer functions of the experimental system and an identified model. Then, disposition of actuators is discussed by using the modal cost analysis. Finally, controllers are designed for SISO and MIMO systems. The feasibility of the proposed controller is verified through numerical simulation and hardware experiments.

A guaranteed deterministic approach to margining on exchange-traded derivatives market: Numerical experiment

2021 ◽  
Vol 57 (4) ◽  
pp. 76
Author(s):  
Sergey Smirnov
Keyword(s):  
Mathematical Model ◽  
Risk Management ◽  
Critical Role ◽  
Deterministic Approach ◽  
Computational Framework ◽  
Modern Approach ◽  
System A ◽  
Lipschitz Constants ◽  
Isaacs Equations ◽  
The Mathematical Model

The article discusses a modern approach to risk management of the central counterparty,primarily the issue of the sufficiency of its financial resources, including the provision of clearingmembers, the capital of the central counterparty and the mutual liability fund. The main subject is the margining system, responsible for an adequate level of collateral for clearing members, that plays critical role in risk management, being the vanguard in protecting against losses associated with default by clearing members and the most sensitive to market risk part of the central counterparty’s skin of the game. A system of margining a portfolio of options and futures in the derivatives market is described, with default management based on the methodology proposed by a number of inventors, registered in 2004. For this system, a mathematical model of margining (i.e. determining the required level of the collateral) is built, based on the ideology of a guaranteed deterministic approach to superhedging: Bellman–Isaacs equations are derived from the economic meaning of the problem. A form of these equations, convenient for calculations, is obtained. Lipschitz constants for the solutions of Bellman–Isaacs equations are estimated. A computational framework for efficient numerical solution of these equations is created. Numerical experiments are carried out on some model examples to demonstrate the efficiency of the system. These experiments also show practical implications of marginsubadditivity — a crucial property of the mathematical model.

scholarly journals Transcranial alternating current stimulation entrains single-neuron activity in the primate brain

2019 ◽  
Vol 116 (12) ◽  
pp. 5747-5755 ◽  
Author(s):  
Matthew R. Krause ◽  
Pedro G. Vieira ◽  
Bennett A. Csorba ◽  
Praveen K. Pilly ◽  
Christopher C. Pack
Keyword(s):  
Human Brain ◽  
Electric Fields ◽  
Critical Role ◽  
Spike Timing ◽  
Model Systems ◽  
Neuron Activity ◽  
Transcranial Electrical Stimulation ◽  
Noninvasive Technique ◽  
Early Results ◽  
Wide Range

Spike timing is thought to play a critical role in neural computation and communication. Methods for adjusting spike timing are therefore of great interest to researchers and clinicians alike. Transcranial electrical stimulation (tES) is a noninvasive technique that uses weak electric fields to manipulate brain activity. Early results have suggested that this technique can improve subjects’ behavioral performance on a wide range of tasks and ameliorate some clinical conditions. Nevertheless, considerable skepticism remains about its efficacy, especially because the electric fields reaching the brain during tES are small, whereas the likelihood of indirect effects is large. Our understanding of its effects in humans is largely based on extrapolations from simple model systems and indirect measures of neural activity. As a result, fundamental questions remain about whether and how tES can influence neuronal activity in the human brain. Here, we demonstrate that tES, as typically applied to humans, affects the firing patterns of individual neurons in alert nonhuman primates, which are the best available animal model for the human brain. Specifically, tES consistently influences the timing, but not the rate, of spiking activity within the targeted brain region. Such effects are frequency- and location-specific and can reach deep brain structures; control experiments show that they cannot be explained by sensory stimulation or other indirect influences. These data thus provide a strong mechanistic rationale for the use of tES in humans and will help guide the development of future tES applications.

Abstract 505: Multiscale mathematical model of skin reveals the critical role of stromal aging in melanoma initiation

2011 ◽  
Author(s):  
Eunjung Kim ◽  
David Basanta ◽  
Vito Rebecca ◽  
Jane Messina ◽  
Rahel Mathew ◽  
...  
Keyword(s):  
Mathematical Model ◽  
Critical Role ◽  
Multiscale Mathematical Model

A Hydrodynamic Efficiency Parameter as a Novel Left Ventricular Diastolic Dysfunction Diagnostic Metric

2008 ◽  
Author(s):  
Kelley C. Stewart ◽  
Rahul Kumar ◽  
John J. Charonko ◽  
Pavlos P. Vlachos ◽  
William C. Little
Keyword(s):  
Diastolic Dysfunction ◽  
Critical Role ◽  
Propagation Speed ◽  
Left Ventricular Diastolic Dysfunction ◽  
Left Ventricular ◽  
Diastolic Filling ◽  
Ventricular Diastolic Dysfunction ◽  
Efficiency Parameter ◽  
Wave Propagation Speed ◽  
The Relationship

Numerous studies have shown that cardiac diastolic dysfunction and diastolic filling play a critical role in dictating overall cardiac health and demonstrated that the filling wave propagation speed is a significant index of the severity of diastolic dysfunction [1, 2]. However, the governing flow physics underlying the relationship between propagation speed and diastolic dysfunction are poorly understood. More importantly, currently there is no reliable metric to allow clinicians the ability to diagnose cardiac dysfunction on the basis of the wave filling speed.

scholarly journals Rational design of minimal synthetic promoters for plants

2020 ◽  
Vol 48 (21) ◽  
pp. 11845-11856 ◽  
Author(s):  
Yao-Min Cai ◽  
Kalyani Kallam ◽  
Henry Tidd ◽  
Giovanni Gendarini ◽  
Amanda Salzman ◽  
...  
Keyword(s):  
Rational Design ◽  
Plant Pathogens ◽  
Critical Role ◽  
Experimental System ◽  
Computational Design ◽  
Regulatory Elements ◽  
Regulatory Function ◽  
Synthetic Promoters ◽  
Sequence Elements ◽  
Plant Promoters

Abstract Promoters serve a critical role in establishing baseline transcriptional capacity through the recruitment of proteins, including transcription factors. Previously, a paucity of data for cis-regulatory elements in plants meant that it was challenging to determine which sequence elements in plant promoter sequences contributed to transcriptional function. In this study, we have identified functional elements in the promoters of plant genes and plant pathogens that utilize plant transcriptional machinery for gene expression. We have established a quantitative experimental system to investigate transcriptional function, investigating how identity, density and position contribute to regulatory function. We then identified permissive architectures for minimal synthetic plant promoters enabling the computational design of a suite of synthetic promoters of different strengths. These have been used to regulate the relative expression of output genes in simple genetic devices.

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