Differences In Wave Speed Research Articles

Dual optical elastography detects -induced alterations in the biomechanical properties of skin scaffolds.

The skin's mechanical properties are tightly regulated. Various pathologies can affect skin stiffness, and understanding these changes is a focus in tissue engineering. Ex vivo skin scaffolds are a robust platform for evaluating the effects of various genetic and molecular interactions on the skin. Transforming growth factor-beta ( ) is a critical signaling molecule in the skin that can regulate the amount of collagen and elastin in the skin and, consequently, its mechanical properties. This study investigates the biomechanical properties of bio-engineered skin scaffolds, focusing on the influence of , a signaling molecule with diverse cellular functions. The receptor I inhibitor, galunisertib, was employed to assess the mechanical changes resulting from dysregulation of . Skin scaffold samples, grouped into three categories (control, -treated, and + galunisertib-treated), were prepared in two distinct culture media-one with aprotinin (AP) and another without. Two optical elastography techniques, namely wave-based optical coherence elastography (OCE) and Brillouin microscopy, were utilized to quantify the biomechanical properties of the tissues. Results showed significantly higher wave speed (with AP, ; without AP, ) and Brillouin frequency shift (with AP, ; without AP, ) in -treated group compared with the control group. The difference in wave speed between the control and + galunisertib with ( ) and without AP ( ) was not significant. Moreover, the + galunisertib-treated group exhibited lower wave speed without and with AP and reduced Brillouin frequency shift than the -treated group without AP, further strengthening the potential role of in regulating the mechanical properties of the samples. These findings offer valuable insights into -induced biomechanical alterations in bio-engineered skin scaffolds, highlighting the potential of OCE and Brillouin microscopy in the development of targeted therapies in conditions involving abnormal tissue remodeling and fibrosis.

High precision improved double-ended travelling wave ranging technology for offshore DC cables

Aiming at the problem of fault location for offshore DC cables, this paper analyses the reasons why the double-ended method is more accurate than the single-ended method in DC transmission lines. We point out that the error in fault location on DC cables using the double-ended method mainly comes from the fact that the difference in wave speed between different segments is ignored. Therefore, based on the traditional double-ended method, this paper proposes an improved double-ended traveling wave ranging method which considers the difference in wave velocity and the actual situation of offshore cables connected in sections using flexible joint technology.

Modal characteristics of sagged-cable-crosstie systems. Part 2: parametric analysis

Analysis of key parameters is an effective means to understanding modal characteristics of a system. However, because of the large number of components, there are various geometric, material, and physical parameters in a sagged-cable-crosstie structure, which inevitably hinders the reasonable selection of key parameters. Based on the companion (Part 1) paper, the effect of four fundamental key parameters, i.e., the Irvine parameter, position and stiffness of crosstie(s), and wave speed ratio, on the modal characteristics of three representative models: double-cable-single-crosstie, three-cable-single-crosstie, and double-cable-double-crosstie, are investigated by mechanical modeling-based parametric analysis. The simultaneous existence of cross-over and veering phenomena that commonly wouldn’t co-exist in single classical cables is found in sagged-cable-crosstie structures. Generally, the frequency curves of all the in-phase modes, out-of-phase modes with symmetrically arranged crossties, and specific out-of-phase modes with crossties just at modal nodes show cross-over phenomena, while that of out-of-phase modes with non-symmetrically arranged crossties show veering phenomena. Setting one or two crossties can only significantly increase the out-of-phase modal frequencies of specific orders, and the increment limits of dimensionless frequency for systems with identical sagged cables are found to be 1 and 2 respectively, no matter how the crosstie stiffness and position are adjusted and how many cables are connected. However, the wave speed difference between sagged cables can enhance the effect of crosstie(s) to further increase modal frequencies, especially for high-order ones, and hence break through the above increment limits. Moreover, the more cables with wave speed differences connected by crossties and the greater the difference in wave speed, the more the system frequency increases.

Transmural Wave Speed Gradient May Distinguish Intrinsic Myocardial Stiffening From Preload-Induced Changes in Operational Stiffness in Shear Wave Elastography.

Shear wave elastography (SWE) is a promising technique to non-invasively assess myocardial stiffness based on the propagation speed of mechanical waves. However, a high wave propagation speed can either be attributed to an elevated intrinsic myocardial stiffness or to a preload-induced increase in operational stiffness. Our objective was to find a way to discriminate intrinsic myocardial stiffening from stiffening caused by an increased pressure in SWE. We used the finite element method to study the shear wave propagation patterns when stiffness and/or pressure is elevated, compared to normal stiffness and pressure. Numerical findings were verified in a few human subjects. The transmural wave speed gradient was able to distinguish changes in intrinsic stiffness from those induced by differing hemodynamic load (a speed of ±3.2 m/s in parasternal short-axis (PSAX) view was associated with a wave speed gradient of -0.17 ± 0.15 m/s/mm when pressure was elevated compared to 0.04 ± 0.05 m/s/mm when stiffness was elevated). The gradient however decreased when stiffness increased (decrease with a factor 3 in PSAX when stiffness doubled at 20 mmHg). The human data analysis confirmed the presence of a wave speed gradient in a patient with elevated ventricular pressure. Cardiac SWE modeling is a useful tool to gain additional insights into the complex wave physics and to guide post-processing. The transmural differences in wave speed may help to distinguish loading-induced stiffening from intrinsic stiffness changes. The transmural wave speed gradient has potential as a new diagnostic parameter for future clinical studies.

Design of multi-material sound transmission blocker using additive manufacturing

Additive manufacturing is most commonly done through 3D printing, which can print in multiple materials. This enables the design and construction of new structures that can block sound transmission, such as a periodic array of TPU plastic cylinders embedded in a matrix of PLA plastic. The difference in wave speed between the plastics can cause reflections and interference inside the material. However, printing in multimaterials provides distinct challenges for the current 3D printing technology. When printing with multiple nozzles, the inactive nozzle can clog, and getting the two materials to fuse can yield warping and separation. We addressed these problems to fabricate a sample of TPU cylinders (1.8 cm diameter, 8.6 cm height) embedded in PLA (20 cm × 10 cm × 2 cm) and measured the change in STL relative to a block of PLA. We discovered an improved attenuation of about 5.5 dB at 6300 Hz.

Applicability of 3D Spectral Element Method for Computing Close-Range Underwater Piling Noises

Pile driving is used for constructing foundation supports for offshore structures. Underwater noise, induced by in-water pile driving, could adversely impact marine life near the piling location. Many studies have computed this noise in close ranges by using semi-analytical models and Finite Element Method (FEM) models. This work presents a Spectral Element Method (SEM) wave simulator as an alternative simulation tool to obtain close-range underwater piling noise in complex, fully three-dimensional, axially-asymmetric settings in the time domain for impacting force signals with high-frequency contents (e.g., frequencies greater than 1000[Formula: see text]Hz).The presented numerical results show that the flexibility of SEM can accommodate the axially-asymmetric geometry of a model, its heterogeneity, and fluid-solid coupling. We showed that there are multiple Mach Cones of different angles in fluid and sediment caused by the difference in wave speeds in fluid, a pile, and sediment. The angles of Mach Cones in our numerical results match those that are theoretically evaluated. A previous work18had shown that Mach Cone waves lead to intense amplitudes of underwater piling noise via a FEM simulation in an axis-symmetric setting. Since it modeled sediment as fluid with a larger wave speed than that of water, we examined if our SEM simulation, using solid sediment–fluid coupling, leads to additional Mach Cones. Because this work computes the shear wave in sediment and the downward-propagating shear wave in a pile, we present six Mach Cones in fluid and sediment induced by downward-propagating P- and S-waves in a pile in lieu of two previously-reported Mach Cones in fluid and sediment (modeled as fluid) induced by a downward-propagating P-wave in a pile. We also showed that the amplitudes of the close-range underwater noise are dependent on the cross-sectional geometry of a pile. In addition, when a pile is surrounded by a solid of an axially-asymmetric geometry, waves are reflected from the surface of the surrounding solid back to the fluid so that constructive and destructive interferences of waves take place in the fluid and affect the amplitude of the underwater piling noise.

Wave intensity analysis in the internal carotid artery of hypertensive subjects using phase-contrast MR angiography and preliminary assessment of the effect of vessel morphology on wave dynamics

Objective: Hypertension is associated with reduced cerebral blood flow, but it is not known how this impacts on wave dynamics or potentially relates to arterial morphology. Given the location of the internal carotid artery (ICA) and risks associated with invasive measurements, wave dynamics in this artery have not been extensively assessed in vivo. This study explores the feasibility of studying wave dynamics in the internal carotid artery non-invasively. Approach: Normotensive, uncontrolled and controlled hypertensive participants were recruited (daytime ambulatory blood pressure <135/85 mmHg and >135/85 mmHg, respectively; n = 38). Wave intensity, reservoir pressure and statistical shape analyses were performed on the right ICA and ascending aorta high-resolution phase-contrast magnetic resonance angiography data. Main results: Wave speed in the aorta was significantly lower in normotensive compared to hypertensive participants (6.7 ± 1.8 versus 11.2 ± 6.2 m s−1 for uncontrolled and 11.8 ± 4.6 m s−1 for controlled hypertensives, p = 0.02), whilst there were no differences in wave speed in the ICA. There were no significant differences between the groups for the wave intensity or reservoir pressure. Interestingly, a significant association between the anatomy of the ICA and wave energy (FCW and size, r2 = 0.12, p = 0.04) was found. Significance: This study shows it is feasible to study wave dynamics in the ICA non-invasively. Whilst changes in aortic wave speed confirmed an expected increase in arterial stiffness, this was not observed in the ICA. This might suggest a protective mechanism in the cerebral circulation, in conjunction with the effect of vessel tortuosity. Furthermore, it was observed that ICA shape correlated with wave energy but not wave speed.

Lung Ultrasound Surface Wave Elastography: A Pilot Clinical Study.

A lung ultrasound surface wave elastography (LUSWE) technique is developed to measure superficial lung tissue elastic properties. The purpose of this paper was to translate LUSWE into clinical studies for assessing patients with interstitial lung disease (ILD) and present the pilot data from lung measurements on 10 healthy subjects and 10 patients with ILD. ILD includes multiple lung disorders in which the lung tissue is distorted and stiffened by tissue fibrosis. Chest radiography and computed tomography are the most commonly used techniques for assessing lung disease, but they are associated with radiation and cannot directly measure lung elastic properties. LUSWE provides a noninvasive and nonionizing technique to measure the elastic properties of superficial lung tissue. LUSWE was used to measure regions of both lungs through six intercostal spaces for patients and healthy subjects. The data are presented as wave speed at 100, 150, and 200 Hz at the six intercostal spaces. As an example, the surface wave speeds are, respectively, 1.88 ± 0.11 m/s at 100 Hz, 2.74 ± 0.26 m/s at 150 Hz, and 3.62 ± 0.13 m/s at 200 Hz for a healthy subject in the upper right lung; this is in comparison to measurements from an ILD patient of 3.3 ± 0.37 m/s at 100 Hz, 4.38 ± 0.33 m/s at 150 Hz, and 5.24 ± 0.44 m/s at 200 Hz in the same lung space. Significant differences in wave speed between healthy subjects and ILD patients were found. LUSWE is a safe and noninvasive technique which may be useful for assessing ILD.

Evaluation of Left Ventricle Systolic and Diastolic Functions by Tissue Doppler Echocardiography in Children with Down Syndrome

Background: Tissue Doppler imaging evaluates the ventricular function in both systolic and diastolic assessments. Objectives: This study aimed to determine the level of cardiac function in children with Down syndrome without structural cardiac lesions using conventional and tissue Doppler echocardiography. Methods: From September 2013 to August 2014 in Mashhad, Iran, a group of 36 children with Down syndrome aged between 4 months and 19 years without anatomic heart disease had their ventricular function assessed by both 2D echocardiography and tissue Doppler imaging. The following were measured: velocity of systolic waves (S), traditional Doppler imaging of early diastolic waves (E), traditional Doppler imaging of late diastolic waves (A), tissue Doppler imaging early diastolic waves (E’), and tissue Doppler imaging late diastolic waves (A’) at the mitral and tricuspid valve levels. Other data, such as fractional shortening, heart rate, and ejection fraction, were also measured. Results: At the time of the examination, the mean age of the participants was 6.4 ± 5.5 years. An association was found between children’s age and the tricuspid A-wave. The A-wave velocity of the tricuspid annulus increased when the body surface area decreased. In addition, compared with the normal subjects, the large age group presented with considerable differences in wave speed, including E, A, and E/E’, at the mitral and tricuspid annulus levels. Conclusions: Despite the Down syndrome children having an apparently normally structured heart, tissue Doppler imaging reveals different findings than those of normal children. The findings of this modality can be used to explain the reason behind the limited physical functioning of children with Down syndrome and may be considered as predictive factors for future cardiac events in these children. © 2016, Growth & Development Research Center.

Determination of Mechanical Properties of Battery Films from Acoustic Measurements

Measuring the mechanical properties of lithium-ion battery films, such as thickness and elasticity, is important for predicting and improving homogeneity of the film and performance of the battery. Problems with film heterogeneity could be identified and addressed early on through accurate, non-destructive inspection of the electrode as it is being manufactured. There are several techniques currently used to measure the mechanical characteristics of films, including nanoindentation and laser-induced surface acoustic waves (SAW). However, their use for analyzing battery electrodes is fairly limited. This research investigates the use of acoustic measurements as an alternative means of non-destructive quality control that could be adapted for on-line use. Mechanical properties of thin films, including elastic modulus and thickness, have been determined using SAW [1,2]. Additionally, acoustic time-of-flight measurements have been taken on complete battery cells to find the state of charge [3]. Here we report on our efforts to measure mechanical properties with SAW. A film under tension is excited to produce a wave. This wave is measured at multiple points along the film to determine the speed of the wave. Because wave dispersion is based on properties such as elasticity and density, we can calculate mechanical properties of the film from the wave speed measurements. Preliminary results indicate that acoustic tests can demonstrate observable differences between films with different properties, and that changes in the stiffness of the film (such as what happens during the drying process for battery films) can also be detected as a difference in wave speed.

Reservoir and reservoir-less pressure effects on arterial waves in the canine aorta.

A time-domain approach to couple the Windkessel effect and wave propagation has been recently introduced. The technique assumes that the measured pressure in the aorta (P) is the sum of a reservoir pressure (Pr), due to the storage of blood, and an excess pressure (Pe), due to the waves. Since the subtraction of Pr from P results in a smaller component of Pe, we hypothesized that using the reservoir-wave approach would produce smaller values of wave speed and intensities. Therefore, the aim of this study is to quantify the differences in wave speed and intensity using P, wave-only, and Pe, reservoir-wave techniques. Pressure and flow were measured in the canine aorta in the control condition and during total occlusion at four sites. Wave speed was determined using the PU-loop (c) and PeU-loop (ce) methods, and wave intensity analysis was performed using P and separately using Pe; the magnitude and time of the main waves and the reflection index were calculated. Both analyses produced similar wave intensity analysis curves, and no significant differences in the timing of the waves, except onset of the forward expansion wave, indicated that distal occlusions have little effect on haemodynamics in the ascending aorta. We consistently found lower values of wave speed and intensities when the reservoir-wave model was applied. In particular, the magnitude of the backward waves was markedly smaller, even during proximal occlusions. In the absence of other independent techniques or evidence, it is not currently possible to decide which of the two models is more correct.

Ca2+ Wave Velocity in Cardiomyocytes is Regulated by Ryanodine Receptor Ca2+ Sensitivity and SR Ca2+ Content

Arrhythmias can be elicited by sudden release of Ca2+ from the sarcoplasmic reticulum (SR) via the SR Ca2+ release channel (RyR) in cardiomyocytes. Such release may initiate a self-propagating process called a Ca2+ wave, which may trigger a spontaneous action potential. We hypothesized that likelihood of arrhythmia is augmented when waves propagate more rapidly, and investigated the role of RyR Ca2+ sensitivity and SR Ca2+ content. Ca2+ waves were studied in isolated ventricular cardiomyocytes from mice using confocal microscopy and Ca2+ fluorescence. Waves preceding spontaneous action potentials propagated more rapidly than those that did not generate action potentials (p<0.05). Thus, mechanisms controlling wave speed may determine arrythmogenic potential. We investigated effects of increased RyR Ca2+ sensitivity by rapidly exposing cells to 1 mM caffeine. The first wave following the switch to caffeine exhibited increased propagation velocity (p<0.05). However, at steady-state, velocity was not altered from pre-treatment values, and mean wave magnitude and SR Ca2+ content were reduced (p<0.05). The opposite intervention, reducing RyR sensitivity with 100 μM tetracaine, increased wave magnitude and SR Ca2+ content at steady state (p<0.05) but did not alter wave speed. These observations suggest that SR content-induced alterations in RyR sensitivity could account for differences in wave speed between initial and steady-state conditions. To test this hypothesis, we increased SR content by pacing cells at 5 Hz, and then stopped the stimulation to allow SR content to decline. Wave speed was observed to progressively decrease following termination of stimulation (p<0.05). Our data suggest that RyR sensitivity and SR Ca2+ content are important determinants of Ca2+ wave speed. An induced increase in RyR sensitivity, possibly relevant in heart failure, increases wave speed only until counteracted by steady-state reduction in SR content.

Visualisation Technique for Trabecular Architecture of Bone Using Ultrasound Signals

We have proposed a new technique for visualising trabecular architecture of spongy bone using ultrasound A-mode signals from a transducer of medical ultrasound system. The technique can be established by finding a method to distinguish between bone and bone marrow. Firstly, the A-mode signal intensity was fitted by the form, A=A0exp(-ax), where A, A0, a, and x represent echo intensity, initial value of echo, attenuation factor, and distance, respectively. Then the curve was moved slightly downward or upward by multiplying with the coefficient k (0.9~1.2), and it was used as an index line to distinguish between bone and bone marrow. To clarify the validity of the proposed technique, we examined bovine bone specimen and a spongy-shaped specimen made by ceramics. The pixel size for creating architecture was 0.2 (width) × 0.15 (depth) mm for bone marrow and 0.2 × 0.3 mm for bone substance, and the pixel size differs due to the difference in wave speeds. The visualisation technique was capable to create an image size of ~10 mm depths from the surface of cortical bone. We also tried to visualise the heel bone.

DEMOGRAPHY AND DISPERSAL: LIFE TABLE RESPONSE EXPERIMENTS FOR INVASION SPEED

Long-distance dispersal has many consequences. One of these is the speed with which a population can invade a new habitat. This invasion wave speed can be calculated from information on demography (in the form of a stage-structured matrix population model) and dispersal (in the form of a distribution of stage-specific dispersal distances). Wave speed complements population growth rate (λ) as an index of population performance in conservation biology. Here we present a new way to calculate the sensitivity of wave speed to changes in short- and long-distance dispersal—indeed, to dispersal at any distance—using the order statistics of the dispersal distribution. This makes it possible to examine the effects of changing the distance dispersed by the longest-dispersing individual, the shortest, the median individual, etc. We apply the method to data on the Pied Flycatcher in the Netherlands, the Starling in the United States, and the Sparrowhawk in England and the Netherlands. We find that wave speed is vastly more sensitive to changes in the uppermost percentiles of the dispersal distribution than to changes elsewhere. The sensitivity results make it possible to carry out life table response experiment (LTRE) calculations, which quantify the contribution of demography, short-distance dispersal, and long-distance dispersal to interpopulation differences in wave speed. We find that 30% of the difference in wave speed between the Pied Flycatcher and the Starling is due to demography and about 70% to dispersal. Most of the dispersal effects come from the top 10% of the dispersal distribution. In contrast, 86% of the difference in wave speed between the two populations of Sparrowhawks is due to differences in demography, and about 14% to differences in dispersal. Again, most of the dispersal effects are due to the upper percentiles of the dispersal distribution. The patterns revealed in the analysis of the four populations are very similar, suggesting that the dependence of wave speed on long-distance dispersal may exhibit common patterns of sensitivity and elasticity.

Acoustical scattering by a density contrast wedge.

Consider the three‐dimensional scattering of a sound pulse generated by an impulsive point source and incident upon a penetrable wedge, identified by a density contrast. The wave speed is common to both regions and the radiation condition of only outgoing waves at infinity is applied in all directions. At the boundary of the wedge there is a pair of transmission conditions which ensure continuity of the acoustic pressure and normal velocity. By using Fourier transforms in time and parallel to the wedge generators and a Kontorovich–Lebedev transform in the radial direction, as described by Jones [Acoustic and Electromagnetic Waves, Oxford (1986)], both the exterior and interior fields can be obtained as a sum of impulsive terms, some of which are due to edge diffraction. If the wedge angle is a rational fraction of π, then the residue series can be summed and, after careful consideration of when and where impulsive disturbances can occur, the fields can be written in remarkably simple closed forms. This solution provides the zero‐order field for a relatively small difference in wave speeds.

Regional pulse wave velocities in hypertensive and normotensive humans

The aim was to compare regional wave transmission and reflection properties along the aorta in age matched normotensive and hypertensive subjects. Simultaneous upstream and downstream micromanometer pressures were recorded at five regions from the ascending aorta to the iliac artery. Recordings were made in the baseline condition in both groups and during sustained isometric handgrip exercise in the normotensives to see if increasing the blood pressure to hypertensive levels would eliminate baseline differences between the two groups. Only subjects who had no coronary or valvular heart disease were studied. Normotensive subjects (n = 8) were selected from those undergoing electrophysiological testing whose blood pressures were consistently in the normal range (systolic less than 140, diastolic less than 90 mm Hg). Age matched hypertensive subjects (n = 17) were those in whom secondary causes of hypertension were excluded and who had repeated measurements of raised blood pressure. In each region pulse wave velocity was estimated from the simultaneous upstream and downstream pressure records using the foot to foot method, and apparent phase velocity was obtained from Fourier analysis of the two pressures. The intensity of wave reflections was judged by the magnitude of fluctuations of the harmonics of apparent phase velocity about the mean of the higher frequency harmonics. In both groups in the baseline state there were regional variations in the pulse wave velocity with the lowest values occurring just proximal to the renal arteries and highest values occurring in the iliac artery. Likewise, in both groups the extent of wave reflections varied regionally--pronounced reflections were seen in the ascending aorta and from just proximal to the renal arteries to the aortic bifurcation but not in the mid-thoracic or iliac regions. The hypertensives had higher pulse wave velocity than normotensives only in the iliac artery (780 v 567 cm.s-1) and had more reflections in the three regions in which reflections were evident. Although handgrip in the normotensive group eliminated regional differences in pulse wave velocity between the groups, reflections were still greater in the hypertensives. Essential hypertension affects the regional properties of the aortic wall. These alterations are manifested by increased peripheral wave-speed and increased wave reflections along the aorta. The differences in wavespeed but not reflection properties are eliminated when the pressures are matched by handgrip, suggesting that factors other than the level of blood pressure per se are responsible for the alterations in reflection properties.

Transient bending waves in plates studied by hologram interferometry

Propagating bending waves are studied in plates made of aluminum and wood. The waves are generated by the impact of a ballistic pendulum. Hologram interferometry, with a double pulsed ruby laser as the light source, is used to record the out of plane motion of the waves. Elliptic-like fringes visualize differences in wave speed for different directions in the anisotropic plate and circular ones are obtained for the isotropic plate. The experimental data for the isotropic plate compare favorably with analytical results derived from the Kirchhoff-plate equation with a point impact of finite duration. A similarity variable is found when starting conditions are modeled as a Dirac pulse in space and time, that brings new understanding to the importance of specific parameters for wave propagation in plates. A formal solution is obtained for a point force with an arbitrary time dependence. For times much larger than the contact time, the plate deflection is shown to be identical to that from a Dirac pulse applied at the mean contact time. A method for determining material parameters, and the mean contact time, from the interferograms is hence developed.

Longitudinal waves in two-layered solid circular cylinder

The method of asymptotic expansions is used to construct a theory of wave-propagation along a solid cylinder made up of two layers of different elastic materials. Wave speed is determined by the ratio of the sum of the area times the effective moduli to that of the area times the densities. However, the effective modulus reduces to Youngs' modulus only if Poisson ratios are equal. The higher approximation, describing dispersive wave-motion, is further affected by the difference in wave-speeds for the two layers. This wave-speed is the ratio of effective modulus to density. The formal expansion is seen to give rise to secular terms. A uniformly valid approximation is given to this order, for the case of a travelling wave.