This study presents a proof-of-concept miniaturized transient elastography (TE) framework for measuring myocardial elasticity during catheter-based cardiac procedures. Recognizing that mechanical properties of myocardial tissue, particularly the shear modulus, offer valuable insight into the development and progression of cardiovascular conditions such as heart failure, we propose a TE system that can be integrated into existing intracardiac catheters. A miniature (2mm×2 mm) piezoelectric actuator was used to generate longitudinal shear waves (LSWs) in tissue-mimicking phantoms with varying shear moduli levels and in ex vivo porcine heart tissue. For validation, an ultrasound array transducer was used in this study to visualize the propagation of the LSWs generated by the actuator. Spatiotemporal displacement maps were analyzed to estimate shear wave speeds and corresponding shear moduli, with TE results showing strong agreement with values obtained using conventional acoustic radiation force-based shear wave elasticity imaging (SWEI). The TE and SWEI measurements showed no statistically significant differences. Ex vivo tissue measurements performed in different orientations relative to myocardial fiber direction confirmed the system's sensitivity to tissue anisotropy. Additionally, the technique successfully distinguished between fresh and fixed heart tissue, detecting a noticeable increase in stiffness due to preservation. These findings support the feasibility of a catheter-integrated TE device as a functional extension of existing clinical workflows, offering quantitative assessment of myocardial elasticity during routine catheterization procedures.

Prediction of shear wave speed in seafloor sediments by integrating geotechnical parameters and interpretable ensemble learning

Assessment of the uncertainty of shear wave speed measurements in ultrasound elastography.

Abstract We study surface capillary-gravity waves for viscous fluid flows governed by Darcy’s law. This includes flows in vertical Hele–Shaw cells and in porous media (the one-phase Muskat problem) with finite or infinite depth. The free boundary is acted upon by an external pressure posited to be in travelling wave form with an arbitrary periodic profile and an amplitude parameter. For any given wave speed, we first prove that there exists a unique local curve of small periodic travelling waves corresponding to small values of the parameter. Then we prove that as the parameter increases but could possibly be bounded, the curve belongs to a connected set C of travelling waves. The set C contains travelling waves that either have arbitrarily large gradients or are arbitrarily close to the rigid bottom in the finite depth case.

In this work, we present a comprehensive analytical and numerical investigation of soliton solutions for a time-fractional [Formula: see text]-dimensional Konopelchenko–Dubrovsky (KD) system describing multidimensional nonlinear wave propagation with memory effects. The model incorporates a modified Riemann–Liouville time-fractional derivative of order [Formula: see text] and accounts for nonlinear interaction, longitudinal and transverse dispersion, and coupling mechanisms. The governing system is [Formula: see text] and by employing a fractional traveling wave transformation, it is reduced to a second-order nonlinear ordinary differential equation describing the wave profile. This reduction preserves the essential balance between nonlinearity, dispersion, and fractional temporal effects, providing a solid foundation for constructing exact solutions. Two complementary analytical techniques, the unified method and the Sardar sub-equation method, are applied to derive multiple families of explicit traveling wave solutions. Several distinct classes of soliton structures, including bright, dark, kink-type, singular, and composite waves, are obtained, illustrating the rich solution space of the fractional KD system. A detailed quantitative analysis is conducted to examine the influence of the fractional order [Formula: see text], wave speed, and dispersion parameters on amplitude, localization, and structural behavior of the solutions. Numerical tabulation allows rigorous assessment of how fractional memory effects modify soliton characteristics compared with the classical integer-order case. The results reveal that fractional dynamics significantly enrich the solution structure of the KD system, yielding a broader spectrum of nonlinear wave patterns and demonstrating the robustness, versatility, and mathematical consistency of the proposed analytical framework. This approach offers a reliable foundation for further theoretical and applied investigations of multidimensional fractional nonlinear wave equations arising in geophysics, fluid dynamics, nonlinear optics, and related applied sciences.

Screening patients with liver fibrosis and identifying those at risk of developing advanced liver fibrosis is of clinical interest. Shear wave elastography (SWE), a promising non-invasive screening tool used to distinguish healthy tissue from diseased tissue, measures tissue shear wave speed (SWS) to describe tissue stiffness and identify liver fibrosis. However, considerable variations in the reported results have been found. We propose that the heterogeneity of the liver tissue background, such as the presence of fatty liver tissue and the preferred local orientation of the scarred fibrotic liver tissues embedded into the liver parenchyma, may contribute to the uncertainty in SWE measurements. Therefore, this study aims to systematically investigate four cofounding factors, the size, volume fraction, and orientation of the fibrotic inclusions, as well as the fatty background, using computer simulations, to describe the multifaceted impact on SWS variability (i.e., SWS standard deviation). The simulations implemented in this preliminary study demonstrated that both fibrosis and fatty background impact the SWS STD and that the SWS STD distributions do not follow a Gaussian distribution. While the SWS STD increased with fibrosis size and volume fraction, the SWS STD decreased as the fatty background increased. The shape of the distribution did not follow a consistent trend across fibrosis inclusion levels, fibrosis sizes, fibrosis orientations, and percent fatty background for either the Mean SWS or the SWS STD. The current study provided evidence that the current clinical guidelines, regarding cut-off values for the different METAVIR Fibrosis stages, overestimate the fibrosis levels in the presence of steatosis.

A benchmark study of 10 different numerical methods for ship motion and load assessment is presented. Pitch motions and midship vertical bending moments are compared to model test results for a containership at zero speed in head regular waves. The wave steepness is varied from 2.1% to 10.5%. The model tests show that pitch and the vertical bending moment (VBM) display nonlinear behavior even for low-steepness waves. It is demonstrated that computational fluid dynamics (CFD) methods can reproduce the ship responses with good accuracy, even in very steep waves, involving green water and parts of the ship going in and out of water. Weakly nonlinear potential-theory methods tend to overestimate the pitch motions and the sagging moments as the wave steepness increases. For the vertical bending moment in steep waves, the 3D panel methods did not give significantly better results than those obtained with the nonlinear strip theories.

While significant progress has been made in analyzing rotating detonation flow fields, research gaps remain in characterizing two-phase flow fields—particularly when integrating the energy conversion process. This study addresses this gap by developing a novel theoretical model that couples the microscopic interaction between detonation waves and kerosene droplets with the macroscopic operation of the combustion chamber. The model explicitly incorporates the energy conversion pathway within the flow field. Results show that in the premixed flow field, detonation combustion accounts for more than half of the combustion in the rotating detonation combustion chamber. When using low activity fuel, the proportion of detonation combustion is relatively small, and the remaining fuel is not burned and exits the combustion chamber with the detonation vortex zone. When using highly active fuels, the proportion of detonation combustion increases, and the detonation vortex zone tends to narrow until it becomes a slip line. For non-premixed flow fields, the discontinuity of the detonation surface will reduce the fuel consumption of detonation combustion, and the proportion of fuel that exits the combustion chamber without combustion will increase. A theoretical formula for calculating the outlet velocity and thrust was proposed and validated, in which the innovation lies in analyzing the rotating detonation flow field for outlet performance enhancement and enabling a degree of prediction for the thrust of rotating detonation waves under varying inflow parameters. The results indicate that the theoretical model demonstrates high accuracy with prediction errors below 1% for wave speed and frequency.

Multilayered soft material characterization using surface wave elastography and laser Doppler vibrometry.

This paper investigates the specific positioning accuracies and uncertainties associated with the measurement of acoustic leakage noise correlation (LNC) in underground pressurized water mains, treating them as acoustic waveguides. It begins by identifying three key intrinsic sources of measurement errors: (1) the speed of acoustic waves in the water mains as influenced by pipe material, wall thickness, modulus of elasticity, and bulk modulus; (2) the distance between the two accelerometers used for correlation; (3) the time delay from the point of leakage to the accelerometers. A mathematical uncertainty model was developed to compute sensitivity coefficients, enabling the propagation of measurement errors from these sources. This was validated through seven sets of full-scale experiments conducted at Q-Leak, a 25,000 sq. ft. test site in Hong Kong. This study ultimately quantified and assessed the contributions of individual error sources to the overall uncertainty, allowing for the prioritization of factors that have the most significant impact in various scenarios. The findings reveal that Young’s modulus and pipe wall thickness are the primary factors affecting measurements for both plastic and metal pipes. Additionally, a universal in-house program, “LNC uncertainty calculator,” was developed to provide insights into the buffer ranges for confirming suspected leak locations while considering constraints within the uncertainty budget. This research highlights the critical but often overlooked area of uncertainty modeling in leak detection for pressurized buried water mains, offering valuable insights intended to enhance operational strategies and maintenance practices within the industry. This research provides a robust framework for understanding the accuracy of leak detection. This means operators can better interpret the reliability of their measurements, leading to consistent decision-making across different situations and minimizing the risk of misidentifying the presence or absence of leakage. In addition, the insights gained from prioritizing factors that affect measurement accuracy allow engineers and operators to make informed decisions about where to focus their resources and efforts. This can lead to more effective maintenance strategies that are tailored to specific conditions, thereby optimizing operational efficiency.

Squeaking is a constant companion in various aspects of our daily lives, whether we slide rubber-soled shoes across hardwood floors1, scrape chalk on a blackboard2, engage the brakes on a bicycle3 or walk with a hip replacement4,5. When two rigid bodies slide over each other, squeaking is widely understood to result from self-excited stick-slip oscillations, triggered by a decrease in the friction coefficient with increasing slip velocity6-10. However, sliding of extended interfaces can involve crack or slip-pulse propagation11-21. This distinction is amplified when a soft body slides on a rigid one, in which large deformations and material mismatch can cause detachment by opening slip pulses22-27. Previous studies focused mainly on slow sliding17,26,28-34, in which pulses are slow and squeaking is absent. Although squeaking at soft-rigid interfaces has been linked to stick-slip oscillations35-37, the mechanisms remain unclear. Here we experimentally investigate soft-rigid interfaces sliding at velocities that produce squeaking. High-speed imaging and acoustic analysis show that opening pulses propagate at approximately the shear wave speed of the soft material, mediating local slip across diverse materials. In flat samples, these pulses are irregular and generate broadband acoustic emissions. Introducing thin surface ridges confines pulse propagation, yielding a consistent repetition frequency matching the first shear mode of the sliding block and squeaking at that frequency. These findings show a structure-driven mechanism that stabilizes rupture in bimaterial friction. Geometric confinement suppresses competing modes, transforming irregular two-dimensional dynamics into coherent one-dimensional pulse trains, offering new insights into frictional rupture from engineered surfaces to geological faults.

Oscillatory instabilities of dynamic fractures arise under mode-I loading as the crack velocity approaches or exceeds the Rayleigh wave speed, c_{R}. Anomalously, at velocities far below c_{R}, experiments reveal a distinct quasistatic oscillatory instability in fluid-driven fracturing of porous materials, formed by continuous bifurcations of "daughter cracks." This phenomenon falls outside the applicability of existing fracture theories. Our asymptotic stability analysis of wave-shaped cracks reveals that oscillations originate from the competition between the stabilizing effect of cohesive force in the process zone and the destabilizing effect of shear perturbations along the crack sides. We further derive the characteristic oscillation wavelength and demonstrate that it is jointly governed by the fracture process and fluid invasion. The findings broaden the physical basis of competing mechanisms governing oscillatory fracture instabilities.

Recent studies have revisited near-sonic and supersonic crack growth, particularly in mode I fractures, challenging the traditional belief that cracks cannot exceed the Rayleigh wave speed ( c R ). While classical fracture mechanics suggest that mode I fractures are limited to c R , recent work shows that cracks can surpass both shear wave velocity ( c S ) and dilatation wave speed ( c P ) under certain conditions. This paper investigates pressure-induced fracturing in porous media, where high fluid injection rates can lead to crack propagation speeds exceeding wave velocities. Using a hybrid peridynamic/finite-element model, where failure and cracks are characterized by a damage model, we simulate the dynamic hydraulic fracture propagation in a rectangular porous domain and explore the influence of fracture energy (related to fracture toughness), permeability, and boundary conditions on crack behavior. Results reveal that forerunning (mother–daughter) fracture events, and mixed lifting-separation and crack-like propagation mechanisms, significantly accelerate crack growth, particularly under low-permeability conditions. We also include a validation of the model through comparison with results from extended finite-element method. These findings have important implications for earthquake rupture dynamics, volcanic activity, and hydraulic fracturing in geophysical applications.

This study presents a comprehensive investigation into the dynamic behaviour of a simply supported static shaft subjected to a rotating force at constant speed, formulated within the framework of Timoshenko beam theory. By employing energy-based methods, the governing system equations are derived and subsequently solved through a combination of Navier’s analytical approach in the spatial domain and Newmark’s numerical integration scheme in the time domain. The primary objective of this research is to identify and analyze the critical speed of peripheral waves generated in shafts under rotary moving forces, a phenomenon that poses significant challenges in the design of high-speed racing car tyres and other advanced mechanical systems. At the critical rotational speed, circumferential flexural waves resonate with the excitation, resulting in a continuous escalation of dynamic response and potential instability. The study further explores the influence of geometric and material parameters, including shaft slenderness ratio, force positioning, and material properties, on the onset of resonance. Comparative validation against existing analytical and numerical studies confirms the accuracy of the proposed methodology and highlights its applicability to practical engineering problems. The results reveal that steel demonstrates the highest critical rotational speed among the three materials examined, thereby reinforcing its suitability for high-speed applications where dynamic stability is essential. Overall, the findings contribute to a deeper understanding of shaft dynamics under rotary excitation and provide valuable insights for the optimization of mechanical components in automotive and aerospace engineering.

In this work, we shall consider Higgs inflationary Einstein–Gauss–Bonnet theories that are compatible with the GW170817 event, which dictates that the gravitational wave speed of primordial tensor perturbations must satisfy the constraint [Formula: see text]. We consider Einstein–Gauss–Bonnet theories that yield directly [Formula: see text] for which theories, the scalar potential and the non-minimal Gauss–Bonnet scalar coupling function are related. We assume that the non-minimal Gauss–Bonnet scalar coupling function is identical with the Higgs potential, and we confront the resulting theory with the ACT data, to determine whether the theory is viable. As we show, the resulting theoretical framework is viable and compatible with the ACT data and the updated Planck constraints on the tensor-to-scalar ratio.

Abstract Spreading waves in electrically excited media is a basic phenomenon that underlines crucial events in many domains, from how electrical signals move through heart tissue to how nerve impulses move through biological neurons. The nonlinear dynamics of electrical excitation and recovery in cardiac tissue give rise to cardiac wave propagation, which is crucial for heart function. FitzHugh-Nagumo (FHN) equation is a prominent mathematical framework for studying this type of excitability. It has been studied in great detail, but complete set of exact solutions that capture its entire broad range of propagation characteristics is still insufficient. To address this limitation, the paper thoroughly develops new exact traveling wave solutions for the FHN equation. The new auxiliary equation method is used for the FHN equation because it can produce a broader and more consistent range of solutions compared to older methods. These solutions reveal a range of nonlinear wave patterns that describe different propagation behaviors in excitable systems, such as solitary, kink-type, and periodic forms etc. The obtained solutions are illustrated using three-dimensional surface plots, density profile plots, and a composite two-dimensional (2-D) configuration, derived from the integration of individual 2-D representations, providing an enhanced understanding of the effect of wave speed. The findings are compared with the outcomes from previously published studies conducted by other researchers. The present method exhibits efficiency, broad applicability, and simplicity in addressing nonlinear evolution equations encountered in mathematical physics and applied sciences.

Passive hyperthermia increases net peripheral and systemic blood flow in humans and other animals, yet the underlying haemodynamic forces that selectively accelerate blood movement remain incompletely characterized. Wave intensity analysis offers insight into the respective contributions of the heart and the vascular system to changes in blood circulation during physiological stress; however, the specific impact of hyperthermia on wave intensity metrics has not been elucidated comprehensively. To address this, we investigated wave speed and wave intensity parameters in the common carotid artery, along with local arterial distensibility in the internal carotid, brachial and common femoral arteries, in addition to total arterial compliance, in eight healthy males across four protocols: (1) 3h of control measurements in normothermic conditions; (2) 3h of one-leg heating; (3) 3h of two-leg heating; and (4) 2.5h of whole-body heating. Forward compression (1.5-fold; P=0.041) and forward expansion (5.2-fold; P<0.0001) waves in the common carotid artery (indices of ventricular contractility and late-systolic blood flow deceleration, respectively) increased exclusively during whole-body heating. In contrast, backward compression waves, wave speed, distensibility and reflection index remained unaltered across all conditions. Notably, distensibility in the major conduit arteries perfusing the brain (internal carotid artery), forearm (brachial artery) and leg (common femoral artery), in addition to total arterial compliance, remained unchanged across all conditions. Collectively, these findings suggest that increases in blood circulation within specific regions of the human body during passive hyperthermia are largely independent of conduit artery mechanics and cardiac performance.

Abstract Snow dampens sounds, but anecdotal reports concisely describe audible propagating collapse events—firnquakes—in Antarctic and Arctic snowfields. We propose combining granular and continuum mechanics to form a testable theory for conditioning, triggering, and propagation of firnquakes consistent with scarce data. A central condition for collapse events is unconsolidated firn at depth. As firn grains compact, stresses are transmitted along force chains which carry the overburden and transition into a continuous medium by pressure sintering. This granular legacy creates solid‐like supports of denser layers that keep the material below unconsolidated. Dynamic amplification triggers local brittle failure of the supports, which induces a cascade of collapse propagation. Using bulk density from ice cores as proxy for stiffness, we find the flexural wave speed by collapsing supports matches the recorded firnquake velocities on the order of 100 m/s. Our theory is to be tested in firn sheets and other compacting granular materials.

Abstract Background Upper urinary tract damage is a danger in patients having neurogenic bladders that cause higher storage pressure due to hypocompliance. Urodynamics is currently regarded as the gold standard for assessing bladder function. However, it is an uncomfortable and invasive investigation that requires catheterization, increasing the chance of infection of the urinary tract. Shear wave elastography (SWE) using acoustic force radiation impulses examination is a non-intrusive ultrasound (US) method that could identify tissue stiffness. Results The study included 20 patients having neurogenic bladder and 20 healthy people as a control group for SWE. Following clinical evaluation and urodynamics in urology department to measure compliance and detrusor pressure (Pdet) in cmH2O, ultrasound shear wave elastography (SWE) on the anterior bladder wall was done, and mean shear wave speed (SWS) was calculated (m/s). The relationship between SWS and Pdet was estimated using Mann–Whitney U test. For comparing mean SWS among research groups, the Chi2 test was utilized. Pdet and mean SWS for urinary bladder anterior wall appeared significantly related, a p value less than 0.001 while r = 0.79, as shown by the correlation matrix. Mean SWS readings were significantly higher among cases compared to controls (2.6 ± 0.7 m/s versus 1.3 ± 0.2, p value less than 0.001 and cutoff point 1.67 m/sec. Conclusion SWE is a promising noninvasive highly sensitive modality in evaluation of neurogenic bladders .

The study investigates the dynamic performance of three-layer cylindrical sandwich shells that contain a concrete core and two nanoclay composite face sheets through vibration testing. Advanced sandwich systems have become popular because their performance improvements stem from two factors, which include enhanced stiffness-to-weight ratios, better damping capabilities, and their ability to control dynamic instability. The first-order shear deformation theory provides the mechanical framework for sandwich shell construction because it accurately models transverse shear deformation in moderately thick shell designs. The Von Kármán strain–displacement relationship establishes geometric nonlinearity for large-amplitude deformations. Hamilton's principle provides a systematic method to derive governing nonlinear equations of motion and boundary conditions for three-layer shell systems. The structure experiences radial external excitation, which allows researchers to study forced vibration and nonlinear dynamic stability of the system. The suitable discretization method converts the nonlinear partial differential equations into a system of nonlinear ordinary differential equations. The Runge-Kutta time integration method delivers numerical solutions that researchers employ to study forced nonlinear wave propagation through different excitation parameters, geometric features, and nanoclay reinforcement. The research studies how cylindrical sandwich shells transmit linear wave motions to measure wave speed through their structural design. The research demonstrates that face sheets that include nanoclay material provide substantial advantages to the concrete-core cylindrical sandwich shell because these face sheets deliver enhanced dynamic stability and vibration control, together with superior wave transmission properties.