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Impact of rescuer position, arm angle, and anthropometric variables on muscle fatigue during cardiopulmonary resuscitation: an international multicentric randomized crossover simulation study

Resuscitation Plus

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Resuscitation Plus 2025年 24卷 100971-100971页

作者： Sa-Couto, Carla Sa-Couto, Pedro Nicolau, Abel Lazarovici, Marc Ericsson, Christoffer Vieira-Marques, Pedro Bispo, Ingrid RISE-Health Community Medicine Information and Decision Sciences Department (MEDCIDS) Faculty of Medicine University of Porto (FMUP) Porto Portugal Center for Research and Development in Mathematics and Applications (CIDMA) Department of Mathematics (DMAT) University of Aveiro Portugal RISE-Health Faculty of Medicine University of Porto Porto Portugal Institut für Notfallmedizin und Medizinmanagement (INM) LMU Klinikum LMU München München Germany Arcada University of Applied Sciences School of Business and Healthcare Helsinki Finland Community Medicine Information and Decision Sciences Department (MEDCIDS) Faculty of Medicine University of Porto (FMUP) Porto Portugal

Background: There is a lack of studies using surface electromyography (sEMG) to objectively assess the impact of rescuer position and arm angle on muscle fatigue during CPR. Additionally, the relationship between anthropometric variables (height and weight) and muscle fatigue remains underexplored. Aim: This study aims to objectively assess muscle fatigue during CPR by analyzing triceps brachii sEMG activation during continuous chest compressions (CCs) across different rescuer positions and arm angles. A secondary objective is to examine correlations between anthropometric variables and muscle fatigue, while also evaluating the impact of CCs quality on fatigue levels. Methods: This international, multicentric, randomized crossover simulation trial included healthcare professionals assigned to one of four rescuer positions: kneeling on the floor, standing, standing on a step stool, and kneeling on a bed. Participants performed two 3-minute trials of continuous CCs at 90° and 105° arm angles. Muscle fatigue was assessed via sEMG, while compression quality was evaluated using manikin-derived data. Results: A total of 72 participants were included. The 105° arm angle significantly increased muscle fatigue compared to 90° (p < 0.001) across all rescuer positions. Taller and heavier rescuers exhibited lower fatigue for both arm angles (p < 0.05);however, fatigue levels were consistently higher at 105° than at 90°. Conclusion: Arm angle is a key determinant of rescuer muscle fatigue, with 105° increasing fatigue compared to 90°. Rescuer position alone was not significant, though fatigue was more pronounced in kneeling and elevated positions. Taller and heavier rescuers demonstrated greater endurance but remained affected by suboptimal arm angles. © 2025 The Authors

关键词： Anthropometric variables Arm angle Cardiopulmonary resuscitation Chest compressions quality Rescuer fatigue Rescuer position Surface electromyography

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A point-free perspective on lax extensions and predicate liftings

arXiv

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arXiv 2021年

作者： Goncharov, Sergey Hofmann, Dirk Nora, Pedro Schröder, Lutz Wild, Paul Friedrich-Alexander-Universität Erlangen-Nürnberg Erlangen Germany Center for Research and Development in Mathematics and Applications University of Aveiro Portugal

In this paper we have a fresh look at the connection between lax extensions and predicate liftings of a functor from the point of view of quantale-enriched relations. Using this perspective, in particular we show that various fundamental concepts and results arise naturally and their proofs become very elementary. Ultimately, we prove that every lax extension is represented by a class of predicate liftings and discuss several implications of this result. © 2021, CC BY.

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Electric traversable wormhole supported by a charged scalar field

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Physical Review D 2024年第6期109卷 064007-064007页

作者： Víctor Jaramillo Mariana Lira Daniel Martínez-Carbajal Darío Núñez Instituto de Ciencias Nucleares Universidad Nacional Autónoma de México Circuito Exterior C.U. A.P. 70-543 Coyoacán México 04510 CdMx 04510 México Department of Astronomy University of Science and Technology of China Hefei 230026 China Departamento de Matemática da Universidade de Aveiro and Centre for Research and Development in Mathematics and Applications (CIDMA) Campus de Santiago 3810-183 Aveiro Portugal

Solving the Einstein-Klein-Gordon-Maxwell system, we construct and analyze the properties of an electrically charged wormhole, formed from a complex, massive scalar field, with self-interaction, and endowed with an electric charge. The scalar field is minimally coupled to the gravitational and the Maxwell field. Covering regions of the value of the different parameters of such wormhole, we present the dependence of the form of the solution with respect to the value of those parameters, emphasizing the role played by the charge in the configurations; we focus on the region for large values of the self-interaction parameter and found a generic behavior of the scalar field, which in turn allows us to determine explicit analytic expressions for the fields, the metric function, and the global quantities such as the Komar mass and the particle number. The motion of charges in these spacetimes is also reported.

关键词： Fluids & classical fields in curved spacetime General relativity General relativity equations & solutions Gravitation Astrophysical electromagnetic fields Numerical relativity

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Gauge structure of the Einstein field equations in Bondi-like coordinates

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Physical Review D 2022年第8期105卷 084055-084055页

作者： Thanasis Giannakopoulos Nigel T. Bishop David Hilditch Denis Pollney Miguel Zilhão Centro de Astrofísica e Gravitação - CENTRA Departamento de Física Instituto Superior Técnico - IST Universidade de Lisboa - UL Av. Rovisco Pais 1 1049-001 Lisboa Portugal Department of Mathematics Rhodes University Grahamstown 6140 South Africa Departamento de Matemática da Universidade de Aveiro and Centre for Research and Development in Mathematics and Applications (CIDMA) Campus de Santiago 3810-183 Aveiro Portugal

The characteristic initial (boundary) value problem has numerous applications in general relativity (GR) involving numerical studies and is often formulated using Bondi-like coordinates. Recently it was shown that several prototype formulations of this type are only weakly hyperbolic. Presently we examine the root cause of this result. In a linear analysis we identify the gauge, constraint, and physical blocks in the principal part of the Einstein field equations in such a gauge, and we show that the subsystem related to the gauge variables is only weakly hyperbolic. Weak hyperbolicity of the full system follows as a consequence in many cases. We demonstrate this explicitly in specific examples, and thus argue that Bondi-like gauges result in weakly hyperbolic free evolution systems under quite general conditions. Consequently the characteristic initial (boundary) value problem of GR in these gauges is rendered ill-posed in the simplest norms one would like to employ. The possibility of finding good alternative norms, in which well-posedness is achieved, is discussed. So motivated, we present numerical convergence tests with an implementation of full GR which demonstrate the effect of weak hyperbolicity in practice.

关键词： General relativity Numerical relativity

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On the Eigenvectors of Generalized Circulant Matrices

arXiv

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arXiv 2023年

作者： Andrade, Enide Carrasco-Olivera, Dante Manzaneda, Cristina Center for Research and Development in Mathematics and Applications Department of Mathematics University of Aveiro 3810-193 Portugal Departamento de Matemática Universidad Del Bío-Bío Avda. Collao 1202 Concepción Chile Departamento de Matemáticas Facultad de Ciencias Universidad Católica Del Norte Av. Angamos 0610 Antofagasta Chile

In this paper, closed formulas for the eigenvectors of a particular class of matrices generated by generalized permutation matrices, named generalized circulant matrices, are *** Codes 15A18, 15A29 Copyright © 20... 详细信息

关键词： Eigenvalues and eigenfunctions

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Epicyclic Frequencies for a Generic Ultracompact Object

arXiv

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arXiv 2022年

作者： Delgado, Jorge F.M. Departamento de Matemática Universidade de Aveiro Center for Research and Development in Mathematics and Applications CIDMA Campus de Santiago Aveiro3810-183 Portugal Centro de Astrofísica e Gravitação - CENTRA Departamento de Física Instituto Superior Técnico - IST Universidade de Lisboa - UL Av. Rovisco Pais 1 Lisboa1049-001 Portugal

Recently, it has been shown that the radial stability of a light-ring (LR) in a spacetime generated by a stationary, axisymmetric, asymptotically flat object with a Z2 symmetry determines the possibility and radial stability of timelike circular orbits (TCOs) around the LR. In this paper, we generalise this result by also considering the vertical (angular) stability of the orbits through the study of the radial and vertical epicyclic frequencies. We show that the vertical stability of the LR only determines the vertical stability of the TCOs around it. A relation between the sum of the squared epicyclic frequencies and the Ricci tensor is also provided. With such relation, we show that objects with radially and vertically unstable LRs (TCOs) violate the null (strong) energy condition. © 2022, CC0.

关键词： Stability

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Scattering by stringy black holes

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Physical Review D 2023年第8期108卷 084060-084060页

作者： Sérgio V. M. C. B. Xavier Carolina L. Benone Luiz C. S. Leite Luís C. B. Crispino Programa de Pós-Graduação em Física Universidade Federal do Pará 66075-110 Belém Pará Brazil Departamento de Matemática da Universidade de Aveiro and Centre for Research and Development in Mathematics and Applications (CIDMA) Campus de Santiago 3810-183 Aveiro Portugal Campus Salinópolis Universidade Federal do Pará 68721-000 Salinópolis Pará Brazil Campus Altamira Instituto Federal do Pará 68377-630 Altamira Pará Brazil

We study the scattering of axially incident massless scalar waves by a charged and rotating black hole solution from heterotic string theory called the Kerr-Sen black hole. We compute the scattering cross section using the partial wave approach, for arbitrary incident wavelengths. We compare our results with those of the general relativistic version of a charged and rotating black hole, namely the Kerr-Newman black hole. We present a selection of numerical results showing that these compact objects have similar scattering properties.

关键词： Classical black holes General relativity Classical solutions in field theory

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Multi-agent systems with memories under DoS attacks

Multi-agent systems with memories under DoS attacks

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International Conference on Control, Automation, Robotics and Vision (ICARCV)

作者： Ricardo Almeida Ewa Girejko Luís Machado Agnieszka B. Malinowska Natália Martins Department of Mathematics Center for Research and Development in Mathematics and Applications University of Aveiro Portugal Faculty of Computer Science Bialystok University of Technology Białystok Poland Institute of Systems and Robotics - University of Coimbra Coimbra Portugal Department of Mathematics University of Trás-os-Montes e Alto Douro (UTAD) Vila Real Portugal

ISBN: (纸本)9781665476881

The paper is devoted to multi-agent systems with memories under denial-of-service (DoS) attacks. The memory is represented by the fractional derivative that appears in the dynamics of the considered systems. The problem that we aim to address is, under which conditions the system continues to be stable or is in consensus mode, despite DoS attacks. Solutions to these problems are proposed in the presented theorems. We strengthen the theoretical considerations with numerical simulations.

关键词： Linear systems Sufficient conditions Automation Denial-of-service attack Numerical simulation Stability analysis Robots

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Estimating data complexity and drift through a multiscale generalized impurity approach

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Journal of Computational mathematics and Data Science 2024年 12卷

作者： Costa, Diogo Rocha, Eugénio M. Ferreira, Nelson Department of Mechanical Engineering University of Aveiro Campus Universitário de Santiago Aveiro 3810-193 Portugal Center for Research & Development in Mathematics and Applications University of Aveiro Campus Universitário de Santiago Aveiro 3810-193 Portugal Department of Mathematics University of Aveiro Campus Universitário de Santiago Aveiro 3810-193 Portugal Bosch Termotecnologia S.A. Aveiro Portugal

The quality of machine learning solutions, and of classifier models in general, depend largely on the performance of the chosen algorithm, and on the intrinsic characteristics of the input data. Although work has been extensive on the former of these aspects, the latter has received comparably less attention. In this paper, we introduce the Multiscale Impurity Complexity Analysis (MICA) algorithm for the quantification of class separability and decision-boundary complexity of datasets. MICA is both model and dimensionality-independent and can provide a measure of separability based on regional impurity values. This makes it so that MICA is sensible to both global and local data conditions. We show MICA to be capable of properly describing class separability in a comprehensive set of both synthetic and real datasets and comparing it against other state-of-the-art methods. After establishing the robustness of the proposed method, alternative applications are discussed, including a streaming-data variant of MICA (MICA-S), that can be repurposed into a model-independent method for concept drift detection. © 2024 The Author(s)

关键词： Classification difficulty Data complexity Data drift Data separability Machine learning

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Can different black holes cast the same shadow?

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Physical Review D 2021年第8期103卷 084040-084040页

作者： Haroldo C. D. Lima Junior Luís C. B. Crispino Pedro V. P. Cunha Carlos A. R. Herdeiro Faculdade de Física Universidade Federal Do Pará Belém PA 66075-110 Brazil Departamento de Matemática da Universidade de Aveiro Centre for Research and Development in Mathematics and Applications (CIDMA) Campus de Santiago Aveiro 3810-183 Portugal

We consider the following question: may two different black holes (BHs) cast exactly the same shadow? In spherical symmetry, we show the necessary and sufficient condition for a static BH to be shadow-degenerate with Schwarzschild is that the dominant photonsphere of both has the same impact parameter, when corrected for the (potentially) different redshift of comparable observers in the different spacetimes. Such shadow-degenerate geometries are classified into two classes. The first shadow-equivalent class contains metrics whose constant (areal) radius hypersurfaces are isometric to those of the Schwarzschild geometry, which is illustrated by the Simpson and Visser (SV) metric. The second shadow-degenerate class contains spacetimes with different redshift profiles and an explicit family of metrics within this class is presented. In the stationary, axi-symmetric case, we determine a sufficient condition for the metric to be shadow degenerate with Kerr for far-away observers. Again we provide two classes of examples. The first class contains metrics whose constant (Boyer-Lindquist-like) radius hypersurfaces are isometric to those of the Kerr geometry, which is illustrated by a rotating generalization of the SV metric, obtained by a modified Newman-Janis algorithm. The second class of examples pertains BHs that fail to have the standard north-south Z2 symmetry, but nonetheless remain shadow degenerate with Kerr. The latter provides a sharp illustration that the shadow is not a probe of the horizon geometry. These examples illustrate that nonisometric BH spacetimes can cast the same shadow, albeit the lensing is generically different.

关键词： Classical black holes Gravitational lenses

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