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Healing outcomes of periodontal and implant-related regenerative procedures are closely related to wound stability, which is partially determined by biomechanical properties and behaviors of oral mucosal tissues. Studies on soft tissue behavior under biomechanical forces in oral regeneration models are scarce. Thus, this review aims to (1) contrast the microstructural differences between the attached gingiva (AM) and lining (LM) mucosa; (2) evaluate biomechanical behaviors of the two mucosal types; and (3) relate residual flap tension to the prevalence of wound opening after regenerative procedures. Compositional and structural differences between the AM and LM explain their biomechanical property differences. Wound destabilizers, including tissue recoil stemming from its viscoelastic property, muscle pull, and inflammatory edema (created after the flap-releasing procedure for primary wound closure) interfere with wound stability. Residual flap tension < 0.05 N is a prerequisite for sustained wound closure. Tissues under stress can exert negative cellular changes, resulting in necrosis and wound dehiscence. Biomechanical properties and the variations between AM and LM dictate the degree of wound stability. Efforts should be made to reduce the negative impact of the potential destabilizers to optimize wound stability. [ABSTRACT FROM AUTHOR]

Synaptic plasticity is important for learning and memory formation; it describes the strengthening or weakening of connections between synapses. The postsynaptic part of excitatory synapses resides in dendritic spines, which are small protrusions on the dendrites. One of the key features of synaptic plasticity is its correlation with the size of these spines. A long-lasting synaptic strength increase [long-term potentiation (LTP)] is only possible through the reconfiguration of the actin spine cytoskeleton. Here, we develop an experimentally informed three-dimensional computational model in a moving boundary framework to investigate this reconfiguration. Our model describes the reactions between actin and actin-binding proteins leading to the cytoskeleton remodeling and their effect on the spine membrane shape to examine the spine enlargement upon LTP. Moreover, we find that the incorporation of perisynaptic elements enhances spine enlargement upon LTP, exhibiting the importance of accounting for these elements when studying structural LTP. Our model shows adaptation to repeated stimuli resulting from the interactions between spine proteins and mechanical forces.

Hydra has a tubular bilayered epithelial body column with a dome-shaped head on one end and a foot on the other. Hydra lacks a permanent mouth: its head epithelium is sealed. Upon neuronal activation, a mouth opens at the apex of the head which can exceed the body column diameter in seconds, allowing Hydra to ingest prey larger than itself. While the kinematics of mouth opening are well characterized, the underlying mechanism is unknown. We show that Hydra mouth opening is generated by independent local contractions that require tissue-level coordination. We model the head epithelium as an active viscoelastic nonlinear spring network. The model reproduces the size, timescale and symmetry of mouth opening. It shows that radial contractions, travelling inwards from the outer boundary of the head, pull the mouth open. Nonlinear elasticity makes mouth opening larger and faster, contrary to expectations. The model correctly predicts changes in mouth shape in response to external forces. By generating innervated : nerve-free chimera in experiments and simulations, we show that nearest-neighbour mechanical signalling suffices to coordinate mouth opening. Hydra mouth opening shows that in the absence of long-range chemical or neuronal signals, short-range mechanical coupling is sufficient to produce long-range order in tissue deformations.

The subject of this study is a nonlinear viscoelastic plate equation with variable exponents and a general source term. Through the application of the Faedo–Galerkin approximation method and a fixed point theorem under appropriate assumptions, we proved the existence of weak solutions. [ABSTRACT FROM AUTHOR]

The electrification of vehicles has emerged as a pivotal technique for addressing environmental concerns and reducing reliance on conventional fuel sources. Conversely, the best way to incorporate renewable energy into electric vehicles (EVs) is still a challenging task, particularly in enhancing the performance of EVs through efficient energy management. The transition to EVs has gained momentum as part of global efforts to mitigate environmental impacts and reduce dependence on fossil fuels. This paper proposes a hybrid method for enhancing EV performance through buck‐boost converters with renewable energy integration. The proposed technique is the joined execution of Flying Foxes Optimization (FFO) and Viscoelastic Constitutive Artificial Neural Networks (vCANNs) techniques. The proposed method's goal is to enhance the energy efficiency, minimize EV charging cost, and mitigating environmental impacts. The renewable energy sources: solar panels, fuel cells, and wind turbines, are integrated into the EV power system through buck‐boost converters. The buck‐boost converter's control signal is optimized through the FFO method. vCANNs are used to predict these control parameters. The proposed strategy is executed in MATLAB software and is compared with existing strategies. In comparison with other current approaches like particle swarm optimization, heap based optimizer, and wild horse optimize, the proposed method achieves a high efficiency of 99% and low cost of 0.05 €/KWh. [ABSTRACT FROM AUTHOR]

BACKGROUND: The rapid and accurate detection of moisture content is important to ensure maize quality. However, existing technologies for rapidly detecting moisture content often suffer from the use of costly equipment, stringent environmental requirements, or limited accuracy. This study proposes a simple and effective method for detecting the moisture content of single maize kernels based on viscoelastic properties. RESULTS: Two types of viscoelastic experiments were conducted involving three different parameters: relaxation tests (initial loads: 60, 80, 100 N) and frequency‐sweep tests (frequencies: 0.6, 0.8, 1 Hz). These experiments generated corresponding force‐time graphs and viscoelastic parameters were extracted based on the four‐element Maxwell model. Then, viscoelastic parameters and data of force‐time graphs were employed as input variables to explore the relationships with moisture content separately. The impact of different preprocessing methods and feature time variables on model accuracy was explored based on force‐time graphs. The results indicate that models utilizing the force‐time data were more accurate than those utilizing viscoelastic parameters. The best model was established by partial least squares regression based on S‐G smoothing data from relaxation tests conducted with initial force of 100 N. The correlation coefficient and the root mean square error of the calibration set were 0.954 and 0.021, respectively. The corresponding values of the prediction set were 0.905 and 0.029, respectively. CONCLUSIONS: This study confirms the potential for accurate and fast detection of moisture content in single maize kernels using viscoelastic properties, which provides a novel approach for the detection of various components in cereals. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Elastomer O-ring seals are used in many technical applications and their requirements are becoming increasingly challenging for high-pressure applications like hydrogen storage systems. We analyze the performance of such seals at low temperatures and highlight the essential effects of primary leakage. Linear viscoelastic material modeling is described and defined with the help of Dynamic Mechanical Thermal Analysis (DMTA), Time-Temperature Superposition Principle (TTSP), and the shift function of Williams-Landel-Ferry (WLF) by assuming thermo-rheological simple material behavior. Numerical calculations and experimental validation are done for strain-rate dependent uniaxial tensile tests, Temperature Retraction (TR), Compression Set (CS), and specific leakage tests with O-rings. Thanks to Finite Element Analysis (FEA) it is possible to identify the most significant influences on the sealing tightness. Thermal shrinkage and the increasingly limited recovery of elastomer O-rings are mainly responsible for primary leakage at low temperatures and can be enforced by time-temperature dependent stress relaxation and manufacturing tolerances. • The elastomer material 80FVMQ 567 was characterized via several material tests. • Linear viscoelastic material modeling was described in detail (WLF, TTSP, Prony) and implemented in the simulation. • Finite element simulations were validated with key O-Ring experiments at different temperatures. • The generation of primary leakage could be shown with numerical analyses and experiments. • The essential effects of primary leakage were identified and segregated with Finite Element Analyses and experiments. [ABSTRACT FROM AUTHOR]

This quest paper covers the most important topic in the field of mechanics. It is the nonlinear viscoelastic wave equations with variable degenerate damping and sources acting in both equations. We seek to prove that this system has no solution with positive initial energy. So, to establish our goal, we utilize the methods and techniques used by Said‐Houari in (J. Nonlinear. Differ. Equ. Appl, vol. 18, 2011, pp. 659‐684.). [ABSTRACT FROM AUTHOR]

The cure‐induced residual stresses have a significant influence on the deformation and mechanical properties of composites. Moreover, the cure‐induced residual stresses exhibit multi‐level and multiscale distributions due to the complexity of micro‐structure of composites and anisotropic characteristics. In this paper, a computationally efficient multiscale procedure is proposed to predict the microscopic residual stresses induced by cure temperature, cure shrinkage and macroscopic residual stresses, which is based to the linear viscoelastic theory combined with the micro‐mechanics method. The instantaneous microscopic residual stresses are expressed as a linear combination of the instantaneous temperature increment, degree of cure increment and macroscopic strain increment at all times of the cure process until to the current time. The proposed method is verified in comparison with the published results in literature and the microscale FEA at different length scales, respectively. The results show that the proposed method is about a thousand times faster than directly using FEA in the microscale RVE model once the influence coefficient matrices are determined. At length, the microscale stresses of all nodes of the entire macroscale model are examined by using the proposed method. It is found that the thermal‐chemical‐mechanical loads lead to serious microscopic stresses for the matrix and interphase constituents, especially for those due to the macroscopic residual stresses. Highlights: Microscale residual stress is written as a linear combination of macroscale loads.Applying macroscale loads on microscale FEA model to obtain influence matrices.The presented model avoids repeatedly FEA microscopic to improve the efficiency.The online time required for the proposed model is much less than microscale FEA.The microscale stress increases the risk of matrix cracking and interface bonding. [ABSTRACT FROM AUTHOR]

This investigation explores the vibrational response of a sandwich plate with material parameter nonhomogeneity and a viscoelastic core, incorporating Pasternak foundations. The study views the equation of motion from an anti-plane shear perspective, presenting a generalized exact dispersion relation (GEDR). It analyzes the impact of parameters like material nonhomogeneity, viscoelasticity, and Pasternak foundation properties on the dimensionless phase velocity against wave number. Findings reveal decreasing phase velocity with increasing wave number, with nonhomogeneity and Pasternak parameters exerting substantial influence. The study offers valuable insights into composite material wave behavior, benefiting design methodologies for diverse applications. [ABSTRACT FROM AUTHOR]

A nonlinear viscoelastic plate equation with logarithmic nonlinearity and variable-exponents is studied. Firstly, the global existence is showed. Next, by using an integral inequality due to Komornik the general decay result is obtained. Finally, the blow-up of solutions is proved with negative initial energy. [ABSTRACT FROM AUTHOR]

Understanding the viscoelastic behavior of pediatric brain tissue is critical to interpret how external mechanical forces affect head injury in children. However, knowledge of the viscoelastic properties of pediatric brain tissue is limited, and this reduces the biofidelity of developed numeric simulations of the pediatric head in analysis of brain injury. Thus, it is essential to characterize the viscoelastic behavior of pediatric brain tissue in various loading conditions and to identify constitutive models. In this study, the pediatric porcine brain tissue was investigated in compression with determine the viscoelasticity under small and large strain, respectively. A range of frequencies between 0.1 and 40 Hz was applied to determine frequency-dependent viscoelastic behavior via dynamic mechanical analysis, while brain samples were divided into three strain rate groups of 0.01/s, 1/s and 10/s for compression up to 0.3 strain level and stress relaxation to obtain time-dependent viscoelastic properties. At frequencies above 20 Hz, the storage modulus did not increase, while the loss modulus increased continuously. With strain rate increasing from 0.01/s to 10/s, the mean stress at 0.1, 0.2 and 0.3 strain increased to approximate 6.8, 5.6 and 4.4 times, respectively. The brain compressive response was sensitive to strain rate and frequency. The characterization of brain tissue will be valuable for development of head protection systems and prediction of brain injury. [ABSTRACT FROM AUTHOR]

Understanding the time-dependent behavior of the rock mass is crucial to improve the reliability of underground structure design, particularly for projects with longer lifespans, such as nuclear waste repositories and hydrocarbon storage tanks. Creep is a time-dependent mechanism that plays a significant role in such designs but is often overlooked. Hence, a comprehensive study of the non-linear viscoelastic response of caverns over extended periods is needed to assess cavern closure under various scenarios. Therefore, this study investigates the time-dependent behavior of caverns constructed in rock-salt and shale rock using a finite element (FE) approach. The analysis was performed by the ABAQUS CAE tool, focusing on an axisymmetric approach. The time-dependent deformation behavior of the rocks was simulated using the Power-Law creep model. Furthermore, a parametric study was carried out to evaluate the influence of overburden depth, shape, volume, and time on the long-term behavior of caverns. The analysis revealed that the excavation of caverns in rock salt resulted in minimal displacements compared to that of shale rock. The results suggested inward displacement at the crown and wall of the cavern, with uplift found at the heel. Furthermore, the augmentation in the volume of the cavern and the depth of the overburden resulted in an enhanced displacement at the wall, crown, and heel of the cavern. Further, the examination of several cavern shapes revealed that spherical caverns show the least displacement compared to cylindrical and horseshoe-shaped caverns. Additionally, the normalized graphs were developed using normalized displacement, rock mass density, overburden depth, and Young's modulus as the basis. Engineers and designers can use these graphs as a useful tool to evaluate the long-term behavior of caverns and make well-informed judgments during the planning stage. Overall, this study contributes to safer and more reliable engineering practices in cavern construction and maintenance by offering insightful information about the time-dependent behavior of rock mass and useful suggestions for enhancing the stability and design of underground structures. [ABSTRACT FROM AUTHOR]

In this paper, we are interested to study the initial value problem for parabolic equations with viscoelastic quantity. These types of equations have many applications in physics. Under some appropriate assumptions of the initial datum, we obtain some regularity results of the solution including upper and lower bounds. We achieve some continuous results of the mild solution according to parameter $ k $. Our study also prove that the mild solution (as well as its derivative) of the parabolic memory problem converges to the solution of the classical parabolic problem. [ABSTRACT FROM AUTHOR]

The viscoelastic behavior of food‐grade biopolymers during gelation has a complex frequency spectrum that is difficult to measure by commercial rheometers. Master curves built by time–temperature superposition (TTS) of data arising from small‐amplitude oscillatory flow (SAOS) or stress relaxation at a given reference temperature can provide the frequency span required to describe the frequency spectrum of highly complex systems such as hydrocolloids (e.g., κappa‐carrageenan). In this work, master curves using TTS were obtained for various concentrations (1%–4% w/w). For a given concentration, mechanical spectra were generated for various temperatures (5, 10, 25, 37, and 45°C) to obtain the master curves and shifting factors (aT, bT) using the WLF (Williams–Landel–Ferry) equation. In this context, a methodology is suggested to obtain a wide observation window to describe complex spectra from gelling systems employed in the chemical industry. Practical applications: The rheological methods used in this work combined the enhancement of the frequency range from experimental stress relaxation and SAOS data with double superposition. These methods are already known, but the combination to achieve an ample frequency range of more than 8 decades represents a useful tool for industrial applications of gelling systems like food hydrocolloids (i.e., κappa‐carrageenan). It also helps to predict the viscoelastic behavior at temperatures and concentrations outside the usual range of rheometric measurements. It is further useful in the areas of equipment design and quality control for food products. [ABSTRACT FROM AUTHOR]

Currently available benchtop (in vitro) aneurysm models are inadequate for testing the efficacy of endovascular device treatments. Specifically, current models do not represent the mechanical instability of giant aneurysms (defined as aneurysms with 25 mm in height or width) and do not predictably rupture under simulated physiological conditions. Hence, in vitro aneurysm models with biomechanically relevant material properties and a predictable rupture timeframe are needed to accurately assess the efficacy of new medical device treatment options. Understanding the material properties of an aneurysm (e.g., shear and compression modulus) as it approaches rupture is a crucial step toward creating a pathologically relevant and sophisticated in vitro aneurysm rupture model. We investigated the change in material properties of a blood vessel, via enzymatic treatment, to simulate the degradation of an aneurysm wall and used this information to create a sophisticated aneurysm rupture model using the latest in additive manufacturing technologies (3D printing) with tissue‐like materials. Mechanical properties (shear and compression modulus) of swine carotid vessels were evaluated before and after incubation with collagenase D enzyme (30 min at 37°C) to simulate the effect of biochemical activity on aneurysm wall approaching rupture compared to control vessels (untreated). Mechanical strength of a soft and flexible 3D‐printed material (VCA‐A30: 30 shore A hardness) was tested for comparison to these arterial vessels. This material was then used to create spherical shaped, giant‐sized (25‐mm diameter) aneurysm phantoms and were run under neurovascular pressures (120/80 ± 5 mmHg), beats per minute (BPM = 70) and flows representing the middle cerebral artery [MCA: 142.67 (±20.13) mL/min] using a blood analog [3.6 (±0.4) cP viscosity] with non‐Newtonian shear‐thinning properties. The shear modulus of swine carotid vessel before treatment was 12.2 (±2.7) KPa and compression modulus was 663.5 (±111.6) KPa. After enzymatic treatment by collagenase D, shear modulus of animal tissues reduced by 33% (p‐value =.039) while compression modulus remained statistically unchanged (p‐value =.615). Control group (untreated vessels) showed minimal reduction (13%, p‐value =.226) in shear modulus and 78% increase (p‐value =.034) in compression modulus. The shear modulus of the 3D‐printed material was 228.59 (±24.82) KPa while its compression modulus was 668.90 (±13.16) KPa. This material was used to prototype a sophisticated in vitro giant aneurysm rupture model. When subjected to physiological pressures and flow rates, the untreated models consistently ruptured at ~12 min. These results indicate that aneurysm rupture can be recreated consistently in a benchtop in vitro model, utilizing the latest 3D‐printed materials, connected to a physiologically relevant programmable pump. Further studies will investigate the optimization of various aneurysm dome thickness regions within the aneurysm, with tunable rupture times for comparison of aneurysm device deployment and benchtop controls based on the measurable effects of pressure and flow changes within the aneurysm models. These optimized in vitro rupture models could ultimately be used to test the efficacy of device treatment options and rupture risk by quantifying specific device rupture times and aneurysm rupture position. [ABSTRACT FROM AUTHOR]

Turbulent flows have been used for millennia to mix solutes; a familiar example is stirring cream into coffee. However, many energy, environmental, and industrial processes rely on the mixing of solutes in porous media where confinement suppresses inertial turbulence. As a result, mixing is drastically hindered, requiring fluid to permeate long distances for appreciable mixing and introducing additional steps to drive mixing that can be expensive and environmentally harmful. Here, we demonstrate that this limitation can be overcome just by adding dilute amounts of flexible polymers to the fluid. Flow-driven stretching of the polymers generates an elastic instability, driving turbulent-like chaotic flow fluctuations, despite the pore-scale confinement that prohibits typical inertial turbulence. Using in situ imaging, we show that these fluctuations stretch and fold the fluid within the pores along thin layers ("lamellae") characterized by sharp solute concentration gradients, driving mixing by diffusion in the pores. This process results in a 3x reduction in the required mixing length, a 6x increase in solute transverse dispersivity, and can be harnessed to increase the rate at which chemical compounds react by 5x--enhancements that we rationalize using turbulence-inspired modeling of the underlying transport processes. Our work thereby establishes a simple, robust, versatile, and predictive way to mix solutes in porous media, with potential applications ranging from large-scale chemical production to environmental remediation. [ABSTRACT FROM AUTHOR]

The present paper is intended to frame-out the analytical approach to study the transference of Love-type waves in a viscoelastic sandy layer sandwiched between a size-dependent consistent couple stress to take care of earth's interior microstructural nature and an orthotropic viscoelastic half-space. An additional parameter termed as characteristic length which is used to investigate the internal microstructural structure of the earth's interior, which provides us the deeper insights of the analysis of wave propagation aspects. With the help of analytical variable separable technique, the closed version of dispersion equation for the Love-type waves has been derived. The impacts of different material parameters like characteristic length (l), sandy parameter (η 2 ′) , viscoelastic parameters (F 1, F 2, F 3), thickness ratio (H 3), and imperfectness parameter (σ 1, σ 2) which are involved in this study are encapsulated by means of graphs on the phase velocity of Love-type waves. Finally, the obtained result is well match up with the classical Love wave equation. This approach of employing micro continuum theories to analyze seismic waves can bring some useful adjustments to previously established facts about seismic waves, as well as improve the applications of micro continuum theories in the field of seismology. [ABSTRACT FROM AUTHOR]

Bio-based composites with passive control layers were investigated by means of a comprehensive set of experiments. The structure, composed of an exterior layer of PLA/Flax and an inserted rubber layer, were manufactured using 3D printing technology. Tensile tests on PLA/Flax and rubber specimens revealed that it exhibited higher stiffness, whereas rubber demonstrated superior elongation. Additionally, three-point bending tests were conducted on 3D-printed composites with varying viscoelastic layer thicknesses (VL) to assess their bending performance. However, the composite with a single 1-mm thick viscoelastic layer (V1t1) showed optimal deflection and stiffness compared to counterparts with different viscoelastic layers. Furthermore, resonance vibration experiments were performed to investigate dynamic parameters such as frequencies and modal loss factors. Based on the experiments, it was determined that V1t1 was the composite that offered the optimal compromise between mechanical and vibration behavior due to its excellent damping characteristics. [ABSTRACT FROM AUTHOR]

Background: Hypercoagulability has been documented in cats with cardiac disease. However, hemostatic parameters, including viscoelastic coagulation monitoring (VCM) have not been reported in cats with arterial thromboembolism (ATE). Hypothesis/Objectives: Compare VCM parameters in cats with acute cardiogenic ATE and in control cats. Animals: Sixteen cats with ATE and 30 control cats. Methods: Multicenter university‐based prospective study. Cardiogenic ATE was diagnosed based on physical examination and by ultrasonographically‐diagnosed left atrial enlargement. Viscoelastic coagulation monitor analysis, CBC, serum biochemistry profile and coagulation profile were performed at admission in cats with ATE. Analysis from healthy control cats was performed using blood collected by direct venipuncture. Our objective was comparison of VCM parameters clot time (CT), clot formation time (CFT), alpha angle (Angle), maximum clot formation (MCF), amplitude at 10 and 20 minutes (A10 and A20, respectively) and clot lysis index at 30 and 45 minutes (LI30 and LI45, respectively) between ATE and control cats. Results: Cats with ATE had a decreased angle compared to control cats, with a median (range) of 43° (30‐48°) compared to 47° (14‐59°; P =.01). The parameters A10, A20 and MCF were decreased in ATE cats compared to control cats with a median (range) of 19 units (8–32) compared to 22 units (6–38), 24.5 units (11‐40) compared to 29 units (10‐47) and 29.5 units (13‐44) compared to 33.5 units (14‐53), respectively (P =.01,.01 and.01, respectively). The parameters CT, CFT, LI30 and LI45 were similar between groups (P =.22,.09,.62 and.34, respectively). Conclusions and Clinical Importance: Cats with cardiogenic ATE cats have VCM parameters consistent with hypocoagulability compared with healthy cats. [ABSTRACT FROM AUTHOR]

Despite the ubiquity and prevalence of rheological consistency across a wide range of industries, there is no clear consensus on its meaning or on one particular technique for quantifying it. Instead, there exist various definitions of "consistency" that are each specific to a given context, and each industry has its own procedure for measuring it. This paper organizes the many subjects and terminologies associated with consistency, providing a comprehensive guide of fundamental mechanics, fundamental properties, modeling techniques, and standardized tests that describe consistency. This includes outlining the rheological models that describe the behavior of viscoelastic and non-Newtonian materials as well as the identification of numerous parameters that can be individually evaluated to comprehensively understand and quantify consistency. Such an understanding of consistency and its underlying mechanical properties encourages the refinement of current consistency test methods and development of new ones. [ABSTRACT FROM AUTHOR]

Abstract Background Hypercoagulability has been documented in cats with cardiac disease. However, hemostatic parameters, including viscoelastic coagulation monitoring (VCM) have not been reported in cats with arterial thromboembolism (ATE). Hypothesis/Objectives Compare VCM parameters in cats with acute cardiogenic ATE and in control cats. Animals Sixteen cats with ATE and 30 control cats. Methods Multicenter university‐based prospective study. Cardiogenic ATE was diagnosed based on physical examination and by ultrasonographically‐diagnosed left atrial enlargement. Viscoelastic coagulation monitor analysis, CBC, serum biochemistry profile and coagulation profile were performed at admission in cats with ATE. Analysis from healthy control cats was performed using blood collected by direct venipuncture. Our objective was comparison of VCM parameters clot time (CT), clot formation time (CFT), alpha angle (Angle), maximum clot formation (MCF), amplitude at 10 and 20 minutes (A10 and A20, respectively) and clot lysis index at 30 and 45 minutes (LI30 and LI45, respectively) between ATE and control cats. Results Cats with ATE had a decreased angle compared to control cats, with a median (range) of 43° (30‐48°) compared to 47° (14‐59°; P = .01). The parameters A10, A20 and MCF were decreased in ATE cats compared to control cats with a median (range) of 19 units (8–32) compared to 22 units (6–38), 24.5 units (11‐40) compared to 29 units (10‐47) and 29.5 units (13‐44) compared to 33.5 units (14‐53), respectively (P = .01, .01 and .01, respectively). The parameters CT, CFT, LI30 and LI45 were similar between groups (P = .22, .09, .62 and .34, respectively). Conclusions and Clinical Importance Cats with cardiogenic ATE cats have VCM parameters consistent with hypocoagulability compared with healthy cats.

This paper addresses a significant research gap in the study of surface waves propagation in a nonhomogeneous, within a magneto-thermoviscoelastic material of higher order, initial stress, rotation, gravity effects and voids. This study provides analytical solutions for surface waves propagating through a medium consisting of a magneto-thermoelastic material with voids under the rotation, electro-magnetic field, gravity field and initial stress. The analytical solutions are derived for the displacement components, volume fraction, temperature to Stoneley and Rayleigh waves are computed numerically and presented graphically considering the external parameters impact. Furthermore, this investigates how magnetic field, voids, gravity, initial stress and fiber-reinforced parameters influence these wave phenomena. This investigation provides valuable insights into the synergistic dynamics among electric constituents, voids, Stoneley and Rayleigh waves propagation, enabling advancements in sensor technology, augmented energy harvesting methodologies, and pioneering seismic monitoring approaches. For certain materials, numerical simulations are provided and graphically displayed. The results of this study reveal several unique cases that significantly contribute to the understanding of Rayleigh and Stoneley waves propagation within this intricate material system, particularly in the presence of voids.

We propose and analyze a simple model for the evolution of an immersed, inextensible filament which incorporates linear viscoelastic effects of the surrounding fluid. The model is a closed-form system of equations along the curve only which includes a 'memory' term due to viscoelasticity. For a planar filament, given a forcing in the form of a preferred curvature, we prove well-posedness of the fiber evolution as well as the existence of a unique time-periodic solution in the case of time-periodic forcing. Moreover, we obtain an expression for the swimming speed of the filament in terms of the preferred curvature. The swimming speed depends in a complicated way on the viscoelastic parameters corresponding to the fluid relaxation time and additional polymeric viscosity. We study this expression in detail, accompanied by numerical simulations, and show that this simple model can capture complex effects of viscoelasticity on swimming. In particular, the viscoelastic swimmer is shown to be faster than its Newtonian counterpart in some situations and slower in others. Strikingly, we even find an example where viscoelastic effects may lead to a reversal in swimming direction from the Newtonian setting, although this occurs when the displacement for both the Newtonian and viscoelastic swimmers is practically negligible. [ABSTRACT FROM AUTHOR]

Toll roads are one of the infrastructure development targets in Indonesia to speed up traffic and vehicle travel times. This paper analyzes the flexible pavement structure of the Yogyakarta-Bawen Toll Road. It predicts damage and residual values using elastic and viscoelastic approaches based on MDPJ Bina Marga 2017 using the KENPAVE Program. The recommended design alternative is pavement with a layer of AC-WC 40 mm, AC-BC 60 mm, Base AC 180 mm, and LPA 300 mm. This alternative is predicted to be able to serve load repetitions in the elastic approach of 432,857,828 ESAL until fatigue cracking occurs, 215,176,089 ESAL until rutting occurs, and 136,575,580 ESAL until permanent deformation occurs. Analysis using the viscoelastic approach can provide load repetitions of 153,304,378 ESAL until fatigue cracking occurs, 47,014,109 ESAL until rutting occurs, and 71,859,938 ESAL until permanent deformation occurs. Based on the elastic approach, the pavement's service life is 33 years, with initial damage in the form of permanent deformation. In comparison, the viscoelastic approach has a service life of 22.7 years, with initial damage in the form of rutting.

Atherosclerosis is one of the most common diseases in the world. Med-ication with metal stents plays an important role in treating this disease. There are many models for delivering drugs from stents to the arterial wall. This paper presents a model that describes drug delivery from the stent coating layers to the arterial wall tissue. This model complements the previous models by considering the mec hanical properties of the arte-rial wall tissue, which changes due to atherosclerosis and improves results for designing stents. The stability behavior of the model is analyzed, and a number of numerical results are provided with explanations. A compar-ison between numerical and experimental results, which examine a more accurate match between the in vivo and in vitro, is shown.

AbstractIn this article, longitudinal wave (P-wave) band structures of functionally graded viscoelastic phononic crystals (PnCs) with exponential distribution properties are analytically investigated via an exact method. Differing from the laminated model, displacement and stress vectors of normal incident P-wave are obtained exactly by utilizing a stress-transform technique and the state space method. According to the continuous condition and Bloch theory, the eigenvalue equation of band structure is derived by applying transfer matrix method. The storage modulus is considered to be frequency-dependent while the loss modulus is neglected for the consideration of components viscoelasticity. Dispersion curves, obtained from the calculation of eigenvalue equation, are validated by the results of exist laminated model and transmission spectra which are also present to reveal the propagation characteristic of normal incident P-wave. Numerical examples indicate that band width and center frequencies of band gaps can be effectively altered by changing magnitude of exponential function, ratio between initial modulus and final modulus. Other new band gaps are opened as well as wider band width are achieved with the increase of gradient index к. The exact analytical solution presented in this paper can be the benchmark for those approximation solutions. [ABSTRACT FROM AUTHOR]

Objective Animal Studied Procedure Conclusion To describe the removal of an adherent, presumed plant‐based, anterior chamber foreign body (ACFB) from the inferior iridocorneal angle in a dog using hydropulsion and ophthalmic viscoelastic device (OVD) capture.A 6‐year‐old female spayed pit bull terrier who was referred for further evaluation of a corneal opacity after being observed running into a thorned succulent plant 1 month earlier. On ophthalmic examination, no corneal foreign body was noted, though mild uveitis was present. Gonioscopy revealed a suspected plant foreign body (thorn tip) in the inferior iridocorneal angle.Under general anesthesia, the ACFB was dislodged from the inferior iridocorneal angle using hydropulsion with balanced salt solution. The superior half of the anterior chamber had been filled with 2% hydroxypropyl methylcellulose OVD to trap the foreign object. One month later, the uveitis had resolved and repeat gonioscopy confirmed the absence of any ACFB in the iridocorneal angle.In the absence of an intraoperative goniolens or endoscopy, hydropulsion and OVD capture of adherent ACFBs may be a feasible option for removal. [ABSTRACT FROM AUTHOR]

Most engineering structures serve in complex and harsh dynamic environments and suffer from nonlinear vibrations generated by random excitations such as strong winds and waves, which need to be mitigated. To this end, a novel viscoelastic nonlinear energy sink (VNES) device is proposed for the vibration control of structures, whereby the random vibration of a nonlinear oscillator with a VNES device is analyzed in this paper. Specifically, the mathematical model of the structure-VNES is formulated. An approximate technique for the treatment of viscoelastic damping element modeled by the fractional derivative is developed, whereby an equivalent nonlinear system without fractional derivative is derived. The averaged Itô equations associated with the amplitude envelopes are then obtained by resorting to the stochastic averaging method. The closed-form solution of the stationary response is solved from the Fokker–Planck–Kolmogorov (FPK) equation and verified by the Monte Carlo simulation (MCS) data simultaneously. The effects of system parameters and noise intensity on the stationary response are sequentially examined. By comparing the VNES system to the case without attachment and one equipped with the commonly used tuned mass damper (TMD) device, the performance and robustness of the VNES are highlighted. The conclusions of this work may contribute to the efficacy of the application of the VNES in practice. [ABSTRACT FROM AUTHOR]

This study aims to describe a toughened adhesive's ratcheting–recovery behavior under reversed cyclic load using a viscoelastic–viscoplastic model. As most adhesives are based on synthetic polymers, their tensile and compression response can be different. A series of load–Sunload tests were conducted on bulk adhesives and bonded joints involving tension/compression–shear loads to characterize the initial yield surface. The effect of hydrostatic stress was studied by considering the instantaneous response and yield strength under tensile and compression loads. Given the observed modulus degradation and extensive permanent strain during reversed cyclic tests, time-dependent damage factors were considered for both viscoelastic and viscoplastic responses. The model was implemented in a finite element (FE) code and used to model the shear response to reversed cyclic load with varying frequency. Good agreement between the model and experiment was obtained. The consideration of both hydrostatic stress and damage was required to describe the observed adhesive reversed cyclic response. [ABSTRACT FROM AUTHOR]

In a bounded domain, we consider a viscoelastic equation utt − ∆u + ∫t0 g(t − τ )∆u(τ )dτ = |u|γ u with a nonlinear feedback localized on a part of the boundary, where γ > 0 and the relaxation function g satisfied g'(t) ≤ ξ(t)gp (t), 1 ≤ p < 3/2, and certain initial data. We establish an explicit and general decay rate result, using some properties of the convex functions. Our new results substantially improve several earlier related results in the literature. [ABSTRACT FROM AUTHOR]

In this paper, the entire downhole fluid-sucker rod-pump system is replaced with a viscoelastic vibration model, namely a third-order differential equation with an inhomogeneous forcing term. Both Kelvin's and Maxwell's viscoelastic models can be implemented along with the dynamic behaviors of a mass point attached to the viscoelastic model. By employing the time-dependent polished rod force measured with a dynamometer as the input to the viscoelastic dynamic model, we have obtained the displacement responses, which match closely with the experimental measurements in actual operations, through an iterative process. The key discovery of this work is the feasibility of the so-called inverse optimization procedure, which can be utilized to identify the equivalent scaling factor and viscoelastic system parameters. The proposed Newton–Raphson iterative method, with some terms in the Jacobian matrix expressed with averaged rates of changes based on perturbations of up to two independent parameters, provides a feasible tool for optimization issues related to complex engineering problems with mere information of input and output data from either experiments or comprehensive simulations. The same inverse optimization procedure is also implemented to model the entire fluid delivery system of a very viscous non-Newtonian polymer modeled as a first-order ordinary differential equation (ODE) system similar to the transient entrance developing flow. The convergent parameter reproduces transient solutions that match very well with those from fully fledged computational fluid dynamics models with the required inlet volume flow rate and outlet pressure conditions. [ABSTRACT FROM AUTHOR]

The present work is the subject of an identification of the viscoelastic behavior of olive wood in creep. Creep bending tests are applied to a cantilever beam fixed at the left end and subjected to a concentrated load at its free end. The applied loads are sufficiently small that they cannot produce viscoplastic strain. A four-parameter viscoelastic model was adopted to reproduce the viscoelastic creep of wood. The elastic modulus is determined directly from the deflection creep curves. It increases with increasing load. The viscoelastic parameters of the studied model are identified using an inverse analysis technique. These parameters increase with increasing load. The test model creep curves show satisfactory consistency. [ABSTRACT FROM AUTHOR]

The long-term aging of bitumens and its effect on low-temperature performance is a detrimental phenomenon. In order to investigate the effects of the aging phenomenon on the low-temperature performance of bitumens, it is very important to accurately simulate the behavior of bitumens in repeated aging cycles and to investigate related viscoelastic, chemical, and microstructural changes. In this research, three types of bitumen with penetration grades of 40/50 , 60/70 , and 85/100 were subjected to one to three cycles of pressure aging vessel (PAV) aging. Comprehensive data on the bitumen's behavior were obtained by conducting bending beam rheometer, Fourier transform infrared spectroscopy, and atomic force microscopy tests. Using the results of the conducted tests, an attempt was made to find precise relationships between different indicators of bitumen aging in terms of chemistry and viscoelasticity. The results revealed a linear correlation between the aging index and the ΔTc and dissipated energy ratio (DER) values, as well as the aging index and the vertical shift factor of the stiffness-time curve. The fitting coefficients of these linear relationships were R2=0.8 and above, indicating a strong linear relationship between these parameters. Furthermore, the viscoelastic indices DER and the derivation of creep compliance (J′) exhibited a fairly good linear relationship. [ABSTRACT FROM AUTHOR]

As they possess the qualities of high specific strength, high specific modulus, high specific energy absorption, and excellent designability, ultra-high molecular weight polyethylene (UHMWPE) fiber-reinforced composites have gradually replaced traditional materials such as ceramics and steel plates as the main ballistic protection materials. Using an improved test method, the uniaxial tensile tests of UHMWPE fiber-reinforced composites at two strain rates of 10−4 s−1 and 10−2 s−1 and a temperature range from −20 °C to 80 °C are carried out to study the effects of strain rate and temperature on the tensile behavior of UHMWPE fiber-reinforced composites. The experimental results indicate that the tensile responses exhibit nonlinear characteristics and the sensitivity of strain rate and temperature. The yield strength and modulus decrease with increasing temperature and increase with the increase in strain rate. A phenomenological viscoelastic constitutive model composed of a nonlinear spring and a nonlinear Maxwell element is proposed to characterize the temperature and strain rate dependent deformation behavior of UHMWPE fiber-reinforced composites before yielding. The results show that the model can accurately predict the tensile nonlinear viscoelastic responses of UHMWPE fiber-reinforced composites before yielding over a wide temperature range under quasi-static loading. [ABSTRACT FROM AUTHOR]

During physiological and pathological processes, cells experience significant morphological alterations with the re-arrangement of cytoskeletal filaments, resulting in anisotropic viscoelasticity. Here, a structure-based cell model is proposed to study the anisotropic viscoelastic mechanical behaviors of living cells. We investigate how cell shape affects its creep responses in longitudinal and perpendicular directions. It is shown that cells exhibit power-law rheological behavior in both longitudinal and perpendicular directions under step stress, with a more solid-like behavior along the longitudinal direction. We reveal that the cell volume and cytoskeletal filament orientation, which have been neglected in most existing models, play a critical role in regulating cellular anisotropic viscoelasticity. The stiffness of the cell in both directions increases linearly with increasing its aspect ratio, due to the decrease of cell volume. Moreover, the increase in the cell's aspect ratio produces the aggregation of cytoskeletal filaments along the longitudinal direction, resulting in higher stiffness in this direction. It is also shown that the increase in cell's aspect ratio corresponds to a process of cellular ordering, which can be quantitatively characterized by the orientational entropy of cytoskeletal filaments. In addition, we present a simple yet robust method to establish the relationship between cell's aspect ratio and cell volume, thus providing a theoretical framework to capture the anisotropic viscoelastic behavior of cells. This study suggests that the structure-based cell models may be further developed to investigate cellular rheological responses to external mechanical stimuli and may be extended to the tissue scale. The viscoelastic behaviors of cells hold significant importance in comprehending the roles of mechanical forces in embryo development, invasion, and metastasis of cancer cells. Here, a structure-based cell model is proposed to study the anisotropic viscoelastic mechanical behaviors of living cells. Our study highlights the crucial role of previously neglected factors, such as cell volume and cytoskeletal filament orientation, in regulating cellular anisotropic viscoelasticity. We further propose an orientational entropy of cytoskeletal filaments to quantitatively characterize the ordering process of cells with increasing aspect ratios. Moreover, we derived the analytical interrelationships between cell aspect ratio, cell stiffness, cell volume, and cytoskeletal fiber orientation. This study provides a theoretical framework to describe the anisotropic viscoelastic mechanical behavior of cells. [Display omitted] [ABSTRACT FROM AUTHOR]

In this paper, we consider a plate viscoelastic p(x)–Kirchhoff type equation with variable-exponent nonlinearities of the form associated with initial and boundary feedback. Under appropriate conditions on p(·), m(·) and q(·), general decay result along the solution energy is proved. By introducing a suitable auxiliary function, it is also shown that regarding negative initial energy and a suitable range of variable exponents, solutions blow up in a finite time. [ABSTRACT FROM AUTHOR]

Over the last half-century, linear viscoelastic models for crack growth in soft solids have flourished but their predictions have rarely been compared to experiments. In fact, most available models are either very approximate or cast in forms which are not quite suitable for the analysis of actual data. Here, we propose a linear viscoelastic approach which consistently exploits the dynamic mechanical analysis data. We apply this method to four sets of results documenting fracture or adhesion rupture in soft solids with various degrees of viscoelasticity. For elastomers, the results reproduce the well-known inconsistency of the process zone size. In more viscoelastic systems, however, the present approach is able to match the measured velocity dependence of the rupture energy with physically acceptable process zone sizes. Moreover, our predictions agree with the damage zone sizes measured by mechanoluminescence. Building on these results, we discuss various issues arising when evaluating the linear viscoelastic contribution to the rupture/adhesion energy in soft solids: data quality, physical interpretation of the parameters, validity of simpler approximations and limitations of the present approach. [ABSTRACT FROM AUTHOR]

Purpose: We aimed at assessing the correlation between TEG reaction time (TEG-R) in citrated and fresh blood samples with TEG5000 and TEG 6S during heparin administration in patients with and without ECMO support. Materials and Methods: Paired TEG5000 (fresh and citrated whole blood, kaolin and kaolin-heparinase) and TEG6S (citrated whole blood) samples were obtained, together with standard coagulation laboratory tests. Bland-Altman analysis and Lin’s concordance correlation coefficient were used to assess agreement. Results: Thirteen consecutive ECMO patients and eight consecutive non-ECMO patients were enrolled and TEG was performed for a total of 84 paired samples. ECMO patients received 19.2 (12.6-25.8) U/kg/h of heparin. Five of the nonECMO patients did not receive heparin, two of them received a very low prophylactic dose (1.6 and 2.9 IU/kg/h, respectively), and one of them 13.1 U/kg/h of heparin. Using TEG®5000, TEG-R was 21.0 (-23.4; 65.5) min longer on fresh compared to citrated blood in patients receiving heparin while only 1.58 (-5.5; 8.7) min longer in patients not-receiving heparin. These differences were reverted by heparinase. Conclusions: Using citrated-recalcified blood to perform TEG might lead to underestimation of the effect of heparin. [ABSTRACT FROM AUTHOR]

This study aims to present an approach for the simulation of ultrasound elastic waves propagation in a diverse range of heterogeneous tissue-like viscoelastic materials, including, but not limited to, Kelvin-Voigt, Zener, Maxwell, Burger's, and Maxwell-Wiechert models, while also allowing for modeling highly viscous fluids. Ultrasound shear wave elastography (SWE) serves as a cost-effective modality for noninvasive, quantitative assessment of soft tissue viscoelastic mechanical properties. To explore tissue viscoelasticity, measuring the shear wave phase velocity in the frequency domain is a common method. In this paper, we employ modeling and numerical simulations to enhance the development of SWE methods. The study employs the staggered grid finite difference (SGFD) method along with recursive calculations of convolution integrals pertinent to linear viscoelastic models. The presented numerical method demonstrates its capability to simulate the propagation of ultrasound elastic waves, both longitudinal and shear, across a broad spectrum of tissue-like viscoelastic heterogeneous materials. The approach successfully accommodates various viscoelastic models without requiring additional modifications in the numerical model, thus enabling a comprehensive exploration of different viscoelastic behaviors commonly observed in diverse tissue types. The developed combination of the SGFD method and recursive calculation of convolution integrals presents a novel and versatile approach in modeling linear viscoelastic tissue-like materials for SWE applications. This method eliminates the need for model-specific adaptations in numerical simulations, thereby offering flexibility for exploring and understanding diverse viscoelastic behaviors inherent in different heterogeneous tissue types, contributing significantly to the advancement of ultrasound SWE for diagnostic purposes. [ABSTRACT FROM AUTHOR]

Understanding viscoelastic behavior of dielectric elastomers for artificial muscle application is important to regulate actuation performance, response time, energy density, sensitivity, duty cycle, etc. The performance of elastomers is widely recognized as being influenced by various fillers, including functional particles and poly-reagents. However, the impact of fillers on the viscoelastic properties of VHB 4910 remains to be fully understood. In this work, a new range of particulate-polymer filled VHB elastomers are studied for the effects of barium titanate and Ketjenblack particles dispersed trimethylolpropane trimethylacrylate on viscoelastic properties. This followed characterization of stress-relaxation and creep behavior to realize the time-dependent mechanical performance. Also, the stress-softening and energy dissipation behavior are examined to find the number of cycles required to reach the equilibrium energy state. Viscoelastic properties of elastomer including elastic modulus, toughness, are found to significantly reduced as a result of modified poroelastic effects due to incorporated fillers. The mechanical properties of composites are evidenced to depend on the size of the particulates and the amount of polymer reagent within elastomer. Theoretical analysis comparing deformation, relaxation, and creep mechanisms in biomedical materials validates the potential of modified elastomers for use in soft actuation devices, particularly in the field of artificial muscles. This work may help in recognizing the strategies to tune viscoelastic behavior of microporous elastomers for potential applications in flexible electronics. [ABSTRACT FROM AUTHOR]

Long‐term service lifetime estimation of soft adhesives is critical for their reliability and durability but is often expensive and time‐consuming. The applicability of the time–temperature superposition principle (TTSP) to predict the shear fatigue life of the soft adhesive was investigated by systematic experiments. Through the analysis of energy dissipation mechanism, it was found that the viscoelastic dissipation stage played a dominant role in the shear fatigue process of the soft adhesive in the lap shear configuration. The master curve of the shear fatigue life at reference temperature could be successfully constructed by using the shift factor obtained from the rheological test. The shear fatigue life at low temperatures could be equivalently predicted based on short‐term testing at relatively high temperatures. The TTSP method is effective in predicting the shear fatigue life of the soft adhesive under wide lifetime ranges and temperatures, which could save testing time and cost greatly. Highlights: Viscoelastic dissipation dominant mechanism exists in the shear fatigue process.The TTSP method is extended to the shear fatigue behavior of soft adhesive.The master curves of the shear creep life and shear fatigue life are constructed.The long‐term service lifetime of soft adhesive obtains an accelerated prediction. [ABSTRACT FROM AUTHOR]

Atherosclerosis is one of the most common diseases in the world. Medication with metal stents plays an important role in treating this disease. There are many models for delivering drugs from stents to the arterial wall. This paper presents a model that describes drug delivery from the stent coating layers to the arterial wall tissue. This model complements the previous models by considering the mechanical properties of the arterial wall tissue, which changes due to atherosclerosis and improves results for designing stents. The stability behavior of the model is analyzed, and a number of numerical results are provided with explanations. A comparison between numerical and experimental results, which examine a more accurate match between the in vivo and in vitro, is shown. [ABSTRACT FROM AUTHOR]

From fundamental research exploring molecular mechanisms to advanced endeavours like the development of artificial white blood cells, white blood cells have widespread applications due to their crucial role in safeguarding the body, defending against infection, and eliminating external pathogens, serving as indicators of several diseases. So, white blood cells must be separated efficiently with high purity to make the passive microdevices more effective for diagnostic applications. In this study, we investigated how cell concentration and viscosity collectively impact the margination of white blood cells in an inertial flow microchannel. We aim to improve white blood cell separation efficiency in microfluidic devices. Unlike previous studies that examined individual factors, this research focused on the interplay between bio-physical properties like cell interaction and viscosity. To explore their correlation, we diluted the blood with phosphate-buffered saline and viscoelastic fluid to manipulate the viscosity and cell concentration. Viscoelastic fluid improved white blood cells margination, while higher viscosity and low cell concentration decreased it. Maintaining blood-like viscosity, optimizing cell-free layer width, and promoting cell-cell interaction in the focusing zone collectively enhanced white blood cells margination.