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Role of ephaptic coupling in discordant alternans domain sizes and action potential propagation in the heart

Physical Review E 2023年第5期107卷 054407-054407页

作者： Niels F. Otani Eileen Figueroa James Garrison Michelle Hewson Laura Muñoz Flavio H. Fenton Alain Karma Seth H. Weinberg School of Mathematical Sciences Rochester Institute of Technology Rochester New York 14623 USA Department of Electrical Computer and Telecommunications Engineering Technology Rochester Institute of Technology Rochester New York 14623 USA Department of Mathematics and Computer Science Hampden-Sydney College Hampden-Sydney Virginia 23943 USA Department of Mathematics and Computer Science Western Carolina University Cullowhee North Carolina 28723 USA School of Physics Georgia Institute of Technology Atlanta Georgia 30332 USA Physics Department and Center for Interdisciplinary Research on Complex Systems Northeastern University Boston Massachusetts 02115 USA Department of Biomedical Engineering The Ohio State University Columbus Ohio 43210 USA

Discordant alternans, the spatially out-of-phase alternation of the durations of propagating action potentials in the heart, has been linked to the onset of fibrillation, a major cardiac rhythm disorder. The sizes of the regions, or domains, within which these alternations are synchronized are critical in this link. However, computer models employing standard gap junction-based coupling between cells have been unable to reproduce simultaneously the small domain sizes and rapid action potential propagation speeds seen in experiments. Here we use computational methods to show that rapid wave speeds and small domain sizes are possible when a more detailed model of intercellular coupling that accounts for so-called ephaptic effects is used. We provide evidence that the smaller domain sizes are possible, because different coupling strengths can exist on the wavefronts, for which both ephaptic and gap-junction coupling are involved, in contrast to the wavebacks, where only gap-junction coupling plays an active role. The differences in coupling strength are due to the high density of fast-inward (sodium) channels known to localize on the ends of cardiac cells, which are only active (and thus engage ephaptic coupling) during wavefront propagation. Thus, our results suggest that this distribution of fast-inward channels, as well as other factors responsible for the critical involvement of ephaptic coupling in wave propagation, including intercellular cleft spacing, play important roles in increasing the vulnerability of the heart to life-threatening tachyarrhythmias. Our results, combined with the absence of short-wavelength discordant alternans domains in standard gap-junction-dominated coupling models, also provide evidence that both gap-junction and ephaptic coupling are critical in wavefront propagation and waveback dynamics.

关键词： Action potential propagation Cardiac dynamics Heart diseases Spiral & scroll waves Coherent structures Heart Traveling waves

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A Survey of Artificial Intelligence Solutions in Response to the COVID-19 Pandemic in Saudi Arabia 18

A Survey of Artificial Intelligence Solutions in Response to...

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18th International Learning and Technology Conference, L and T 2021

作者： Aljizawi, Jailan Dalloul, Dina Ghryani, Layal Aldabbagh, Shaymaa Brahimi, Tayeb Computer Science Department College of Engineering Effat University Jeddah Saudi Arabia Energy and Technology Research Center Natural Science Mathematics and Technology Unit College of Engineering Effat University Jeddah Saudi Arabia

Artificial Intelligence (AI) has a significant impact on the course of the COVID-19 pandemic from various aspects. This paper aims to explore the trends of AI applications and how they help predict and prevent the progress of COVID-19 in Saudi Arabia. The method used in this study is based on a narrative review of recent literature on AI and COVID-19 and on a survey conducted on 211 participants. Results show that AI is a crucial element to overcoming COVID 19. The use of COVID-19 related Apps that helped reduce the pandemic spread was more common among the age group participants ranging from 15 - 30. The study concluded that COVID-19 made a positive impact on everyone, and by the use of technology, things got much more comfortable to help in enduring any long-term health consequences. © 2021 The Authors. Published by Elsevier B.V.

关键词： COVID-19

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Experimental and numerical investigation of dissimilar weld characterization in laser welding of duplex 2205 and AISI 1060 steel: Microstructure, mechanical properties and weld geometry

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Heliyon 2024年第24期10卷 e40899页

作者： Botlani Esfahani, Mohammad Behzad Karimipour, Arash Akbari, Mohammad Abdollahi, Ali Najafi, Mohammad Department of Mechanical Engineering Najafabad Branch Islamic Azad University Najafabad Iran Aerospace and Energy Conversion Research Center Najafabad Branch Islamic Azad University Najafabad Iran Department of Mechanics Electrical Power and Computer Science and Research Branch Islamic Azad University Tehran Iran Modern Automotive Research Center Science and Research Branch Islamic Azad University Tehran Iran

Dissimilar laser welding of martensitic AISI 1060 carbon steel and Duplex Stainless Steel 2205 was performed based on an experimental and numerical study. The experiments were then conducted based on central composite design experiments (CCD) and analyzed via the response surface methodology (RSM) by considering the effect of laser welding process parameters (incident laser power, speed of welding, nozzle distance and deviation of laser beam) on the weld joint characterization. The experimental results showed that the laser power had a remarkable effect on the melt pool depth. By increasing the laser power from 250 to 450 W at the focal point position, the melt pool depth was increased from 0.4 to 1.4 mm. The microstructure of the molten pool was mainly composed of the solidification of duplex stainless steel (DSS). The molten pool microstructure included columnar dendritic and inter-dendritic microstructures at the boundary fusion line of the toward duplex 2205 base metal. The cellular microstructure with epitaxial grain growth at the center of the molten pool was then formed. According to the numerical simulation results, by increasing the laser power from 250 to 400 W, the extension of high temperature region (more than 1800 °C) was raised to about 150 percent at both depth and width. According to the tensile tests results, the joint fracture surface of the carbon steel side of the joint showed a brittle fracture mechanism due to the martensitic nature of the microstructure of carbon steel, while the fracture cross-section of the DSS side of the joint had a mostly ductile fracture mode, as compared to carbon steel. By increasing the laser beam energy density to more than 0.05 MW/cm2, a coarse grain cellular dendrite was formed at the fusion zone toward AISI 1060 steel along with tempered martensitic microstructure at the heat affected zone of the AISI1060 base metal. This led to the transformation of the joint fracture mechanism from a brittle one to a ductile on

关键词： AISI 1060 carbon steel Dissimilar laser welding Duplex stainless steel 2205 Microstructural changes Response surface methodology (RSM) Weld characterizations

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Database management system design for automatic weather information with twitter data collection 6

Database management system design for automatic weather info...

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6th International Conference on Information Management and Technology, ICIMTech 2021

作者： Purwandari, Kartika Perbangsa, Anzaludin Samsinga Sigalingging, Join W. C. Krisna, Adhi Asta Anggrayani, Suci Pardamean, Bens Bina Nusantara University Bioinformatics and Data Science Research Center Jakarta11480 Indonesia Bina Nusantara University School of Information Systems Information Systems Department Jakarta11480 Indonesia Meteorological Climatological and Geophysical Agency Database Center Division of Bmkg Jakarta10720 Indonesia Bina Nusantara University Binus Graduate Program - Master of Computer Science Computer Science Department Jakarta11480 Indonesia

ISBN: (纸本)9781665449373

Improvement of data management about weather in Indonesia is very supportive of the need for weather information. Currently, the weather information that is disseminated to the public is only based on sensor location points that are spread across Indonesia. However, supporting data generated from these sensors is only limited to certain areas. We hence develop a database system that can help collect weather information automatically via Twitter. This facilitates the Indonesian people in knowing weather information based on the completeness of data from sensor data and Twitter. The steps from the database that are built will be very helpful in collecting data about the weather throughout Indonesia. The basic step that we use in our database are conceptual, logical and physical design. The information obtained in this study is very important for efficient and effective data collection to achieve real-time automation of weather information. © 2021 IEEE.

关键词： Database systems

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Robust Co-Design of Canonical Underactuated Systems for Increased Certifiable Stability

Robust Co-Design of Canonical Underactuated Systems for Incr...

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IEEE International Conference on Robotics and Automation (ICRA)

作者： Federico Girlanda Lasse Shala Shivesh Kumar Frank Kirchner Robotics Innovation Center German Research Center for Artificial Intelligence (DFKI GmbH) Bremen Germany Department of Information Engineering University of Padova Italy Department of Mechanics & Maritime Sciences Dynamics Division Chalmers University of Technology Gotheburg Sweden Faculty of Mathematics and Computer Science University of Bremen Bremen Germany

ISBN: (数字)9798350384574

ISBN: (纸本)9798350384581

Optimal behaviours of a system to perform a specific task can be achieved by leveraging the coupling between trajectory optimization, stabilization, and design optimization. This approach is particularly advantageous for underactuated systems, which are systems that have fewer actuators than degrees of freedom and thus require for more elaborate control systems. This paper proposes a novel co-design algorithm, namely Robust Trajectory Control with Design optimization (RTC-D). An inner optimization layer (RTC) simultaneously performs direct transcription (DIRTRAN) to find a nominal trajectory while computing optimal hyperparameters for a stabilizing time-varying linear quadratic regulator (TVLQR). RTC-D augments RTC with a design optimization layer, maximizing the system’s robustness through a time-varying Lyapunov-based region of attraction (ROA) analysis. This analysis provides a formal guarantee of stability for a set of off-nominal states. The proposed algorithm has been tested on two different underactuated systems: the torque-limited simple pendulum and the cart-pole. Extensive simulations of off-nominal initial conditions demonstrate improved robustness, while real-system experiments show increased insensitivity to torque disturbances.

关键词： Couplings Torque Regulators Stability analysis Robustness Task analysis Robotics and automation

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A Robust Semantic Communication System for Image Transmission

A Robust Semantic Communication System for Image Transmissio...

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IEEE Conference on Global Communications (GLOBECOM)

作者： Xiang Peng Zhijin Qin Xiaoming Tao Jianhua Lu Khaled B. Letaief Department of Electronic Engineering Tsinghua University Beijing China Beijing National Research Center for Information Science and Technology (BNRist) Beijing China State Key Laboratory of Space Network and Communications Beijing China Department of Electronic and Computer Engineering Hong Kong University of Science and Technology Hong Kong China

ISBN: (数字)9798350351255

ISBN: (纸本)9798350351262

Semantic communications have gained significant attention as a promising approach to address the transmission bottleneck, especially with the continuous development of 6G techniques. Distinct from the well investigated physical channel impairments, this paper focuses on semantic impairments in images, particularly those arising from adversarial perturbations. Specifically, we propose a novel metric for quantifying the intensity of semantic impairment and develop a semantic impairment dataset. Furthermore, we introduce a deep learning enabled semantic communication system, termed as DeepSC-RI, to enhance the robustness of image transmission, which incorporates a multi-scale semantic extractor with a dual-branch architecture for extracting semantics with varying granularity, thereby improving the robustness of the system. The fine-grained branch incorporates a semantic importance evaluation module to identify and prioritize crucial semantics, while the coarse-grained branch adopts a hierarchical approach for capturing the robust semantics. These two streams of semantics are seamlessly integrated via an advanced cross-attention-based semantic fusion module. Experimental results demonstrate the superior performance of DeepSC-RI under various levels of semantic impairment intensity.

关键词： Measurement Image communication Perturbation methods Semantics Rician channels Semantic communication Transformers Robustness Streams Signal to noise ratio

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Learning Generalized Hamiltonians using fully Symplectic Mappings

arXiv

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arXiv 2024年

作者： Choudhary, Harsh Gupta, Chandan Kungrutsev, Vyacheslav Leok, Melvin Korpas, Georgios Department of Computer Science Czech Technical University Prague Czech Republic Indraprastha Institute of Information Technology Delhi India Department of Mathematics UC San Diego CA92093 United States Quantum Technologies Group HSBC 117439 Singapore Archimedes Research Unit on AI Data Science and Algorithms Athena Research Center Marousi15125 Greece

Many important physical systems can be described as the evolution of a Hamiltonian system, which has the important property of being conservative, that is, energy is conserved throughout the evolution. Physics Informed Neural Networks (PINNs) and in particular Hamiltonian Neural Networks (HNNs) have emerged as a mechanism to incorporate structural inductive bias into the NN model. By ensuring physical invariances are conserved, the models exhibit significantly better sample complexity and out of distribution accuracy than standard NNs. Learning the Hamiltonian as a function of its canonical variables, typically position and velocity, from sample observations of the system thus becomes a critical task in system identification and long-term prediction of system behavior. However, in order to truly preserve the long run physical conservation properties of Hamiltonian systems, one must use symplectic integrators for a forward pass of the system’s simulation. While symplectic schemes have been used in the literature, they are thus far limited to situations when they reduce to explicit algorithms, which include the case of separable Hamiltonians or augmented non-separable Hamiltonians. In general, symplectic integrators are implicit in nature, making backpropagation challenging. Noting the self-adjoint property of symplectic integration, we propose a method for incorporating one integrator for the forward and backward pass in order to perform training on the NN trajectories. We use a predictor-corrector method to warm start the procedure, easing the computational challenges of solving an implicit symplectic integrator. We show that the method is robust to noise and provides a good approximation of the system Hamiltonian when the state variables are sampled from a noisy observation. Our method unlike previous works assumes a single generic Hamiltonian structure which after training can be used to capture long-term behavior of systems governed by complex dynamics as well as

关键词： Hamiltonians

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Cognitive Radio-Based Spectrum Sensing for Dynamic Spectrum Access in Sensor Ad Hoc Networks

Cognitive Radio-Based Spectrum Sensing for Dynamic Spectrum ...

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International Conference on Computing and Networking Technology (ICCNT)

作者： B. Geetha Amit Kansal Gadug Sudhamsu Piyush P. Gawali A. Amudha Bhavuk Samrat Department of Science and Humanities Prince Shri Venkateshwara Padmavathy Engineering College Chennai Quantum University Research Center Quantum University Uttar Pradesh India School of Engineering and Technology Computer Science and Engineering JAIN (Deemed to be University) Bangalore Karnataka Department of Computer Engineering Vishwakarma Institute of Technology Pune INDIA Department of Electrical and Electronics Engineering Karpagam Academy of Higher Education Coimbatore Centre for Interdisciplinary Research for Business and Technology Chitkara University Institute of Engineering and Technology Chitkara University Punjab India

ISBN: (数字)9798350370249

ISBN: (纸本)9798350370270

Cognitive Radio-primarily based Spectrum Sensing (CRSS) is a crucial generation for permitting dynamic spectrum access in sensor ad hoc networks (SAHNs). This era allows customers to successfully make use of to be had spectrum whilst keeping off interference from existing customers. CRSS makes use of sensing and optimization strategies to identify free frequency bands to enable verbal exchange in SAHNs. Moreover, the CRSS additionally consists of protocols and techniques to locate and defend against malicious behavior, which include spectrum jamming and false sensing reports. Subsequently, CRSS may be blended with superior technology, such as multi-agent structures and system gaining knowledge of, to create an efficient and sturdy gadget for dynamic spectrum access.

关键词： Protocols Accuracy Heuristic algorithms Electricity Dynamic spectrum access Interference Ad hoc networks Sensors Jamming Optimization

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Cavity-driven ultrafast chiral optical switching 8

Cavity-driven ultrafast chiral optical switching

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2D Photonic Materials and Devices VIII 2025

作者： Zhou, Lingxiao Liu, Bin Liu, Yuze Lu, Yang Li, Qiuyang Xie, Xin Lydick, Nathanial Hao, Ruofan Liu, Chenxi Watanabe, Kenji Taniguchi, Takashi Chou, Yu-Hsun Forrest, Stephen R. Deng, Hui Department of Physics University of Michigan 450 Church Street Ann ArborMI48109-2122 United States Department of Electrical Engineering and Computer Science University of Michigan 1301 Beal Avenue Ann ArborMI48109-2122 United States Applied Physics Program University of Michigan 450 Church Street Ann ArborMI48109-2122 United States Nuclear Engineering and Radiological Science University of Michigan 2355 Bonisteel Blvd Ann ArborMI48109-2122 United States Research Center for Electronic and Optical Materials National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan Research Center for Materials Nanoarchitectonics National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan Department of Photonics National Cheng Kung University Tainan Taiwan Academy of Innovative Semiconductor and Sustainable Manufacturing National Cheng Kung University Tainan Taiwan

ISBN: (纸本)9781510684843

Floquet engineering, where an oscillating electric field modifies quantum states, is a promising tool to manipulate quantum systems coherently. For example, the valley-selective A.C. Stark effect can break time-reversal symmetry in monolayer transition metal dichalcogenides by lifting valley degeneracy. However, Floquet engineering has often been limited by the requirement of an ultrashort optical pulse with a high enough pulse energy. Here, based on a cavity structure with monolayer WSe2, we demonstrate that cavity effects can enhance effective Floquet dressing power by orders of magnitude. The strong enhancement also enables us to build an efficient chirality all-optical switch by the Floquet effect. Our study opens up the possibility to exploit Floquet engineering and other nonlinear phenomena for efficient optical devices of low-dimension materials. © 2025 SPIE.

关键词： Stark effect

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Scalable Face Image Coding via StyleGAN Prior: Towards Compression for Human-Machine Collaborative vision

arXiv

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arXiv 2023年

作者： Mao, Qi Wang, Chongyu Wang, Meng Wang, Shiqi Chen, Ruijie Jin, Libiao Ma, Siwei The School of Information and Communication Engineering The State Key Laboratory of Media Convergence and Communication Communication University of China Beijing100024 China The Department of Computer Science City University of Hong Kong Hong Kong The National Engineering Research Center of Visual Technology School of Computer Science Peking University Beijing100871 China

The accelerated proliferation of visual content and the rapid development of machine vision technologies bring significant challenges in delivering visual data on a gigantic scale, which shall be effectively represented to satisfy both human and machine requirements. In this work, we investigate how hierarchical representations derived from the advanced generative prior facilitate constructing an efficient scalable coding paradigm for human-machine collaborative vision. Our key insight is that by exploiting the StyleGAN prior, we can learn three-layered representations encoding hierarchical semantics, which are elaborately designed into the basic, middle, and enhanced layers, supporting machine intelligence and human visual perception in a progressive fashion. With the aim of achieving efficient compression, we propose the layer-wise scalable entropy transformer to reduce the redundancy between layers. Based on the multi-task scalable rate-distortion objective, the proposed scheme is jointly optimized to achieve optimal machine analysis performance, human perception experience, and compression ratio. We validate the proposed paradigm’s feasibility in face image compression. Extensive qualitative and quantitative experimental results demonstrate the superiority of the proposed paradigm over the latest compression standard Versatile Video Coding (VVC) in terms of both machine analysis as well as human perception at extremely low bitrates ( © 2023, CC BY-NC-ND.

关键词： Image coding

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