Changes In Wave Velocity Research Articles

Abstract MP60: A Randomized Placebo-Controlled Trial of Pitavastatin Calcium to Treat Combined Dyslipidemia of Obesity in Adolescents - The Pediatric Heart Network Dyslipidemia of Obesity Intervention in Teens (Do It!) Trial

Background: Combined dyslipidemia of obesity (CDO) is prevalent in ~20% of youth and characterized by high numbers of atherogenic small LDL (sLDL) particles associated with stiffer arteries. The safety and impact of statin therapy is not known. Methods: A 2-year masked trial of pitavastatin calcium 4 mg/day versus placebo for participants ages 10-19 years with body mass index (BMI) ≥85 th %ile and CDO defined as non-HDL-C ≥120 mg/dL and either low HDL-C or high triglyceride (TG):HDL-C ratio. The primary outcome was change in carotid-femoral pulse wave velocity (PWV) and carotid measures assessed at baseline, 6, 12, 18, and 24 months. Secondary outcomes included safety and lipid measures. Results: Across 18 sites, 59 participants were randomized to pitavastatin and 60 to placebo. Demographic (mean age 13.5±1.2 yrs; 55% males), anthropomorphic (BMI %ile 98±3; waist/height ratio 0.66±0.08), lipid (non-HDL-C 167±29 mg/dL, LDL-C 127±25 mg/dL, HDL-C 37±7 mg/dL, TG/HDL ratio 6.4±4.7, sLDL number 866±419 nmol/L), vascular (PWV 5.0±0.7 m/sec) and safety measures were similar at baseline between groups. There were 28 early terminations (11 pitavastatin, 17 placebo). Significant reductions with pitavastatin versus placebo were noted in non-HDL-C (median -25% vs +3% at 6 months, p<0.001), LDL-C (-29% vs +7%, p<0.001), and apolipoprotein B (-26% vs 0%, p<0.001). An early reduction relative to placebo in sLDL particle number was not sustained (FIGURE A), and there were no significant changes or trends for PWV (FIGURE B) or carotid measures in either group. There was one serious adverse event (placebo), and no significant differences in liver enzymes, muscle toxicity, glucose homeostasis, or somatic growth, including adiposity. Conclusions: Over 2 years, treatment of CDO in adolescents with pitavastatin calcium resulted in significant improvement in dyslipidemia with no safety concerns. No change in PWV in either group may be due to lower-than-expected baseline PWV, insufficient magnitude of impact on CDO, or lack of change in adiposity.

Ultrasonic monitoring of softening in solid foods during in-vitro gastric digestion

This study aims to evaluate the feasibility of using non-destructive ultrasound to monitor textural softening in potato and cheese during in vitro gastric digestion. Textural measurements were taken after different digestion times (5, 10, 15, 20, 25, 30, 60, 90, and 120 min) at 37 °C, while in vitro digestion was non-destructively monitored using ultrasound in through-transmission mode.The textural softening resulted in a substantially greater variation in hardness, ranging from 0.418 to 1.241 N for potato and from 0.200 to 0.534 N for cheese. Meanwhile, the ultrasonic velocity increased during gastric digestion from 745 ± 106.6 m/s to 1342.9 ± 131.5 m/s in potato and from 1377.4 ± 3.8 m/s to 1502.8 ± 4.6 m/s in cheese. Both the softening and velocity increase were attributable to the compositional variation occurring within the food structure due to gastric fluid diffusion into the food matrix. The Weibull model kinetic parameter “k” indicated that potato exhibited a higher softening rate than cheese, due to a faster gastric fluid migration. This was also evidenced by the effective diffusivity of gastric fluid (Deff) obtained by modeling the evolution of the ultrasonic velocity during digestion (Deff, potatõ2.5 Deff, cheese). A noticeable relationship was found between the softening of both food matrices and the change in the ultrasonic wave velocity. Additionally, it should be highlighted that the measurement of the ultrasonic velocity by ultrasound presented a lower degree of variability than instrumental texture assessment. Therefore, ultrasound proves to be an accurate technique for the on-line monitoring of textural changes in foods during in vitro digestion. This non-destructive approach provides a powerful instrumental tool in the design of new products with enhanced nutritional properties by better monitoring how in vitro digestion affects their mechanical properties.

Stress‐induced anisotropy in Gulf of Mexico sandstones and the prediction of in situ stress

AbstractThe strong sensitivity of velocity to stress observed in many sandstones originates from the response of stress‐sensitive discontinuities such as grain contacts and microcracks to a change in effective stress. If the change in stress is anisotropic, then the change in elastic wave velocities will also be anisotropic. Characterization of stress‐induced elastic anisotropy in sandstones may enable estimation of the in situ three dimensional stress tensor with important application in solving problems occurring during drilling, such as borehole instability, and during production, such as sanding and reservoir compaction. Other applications include designing hydraulic fracture stimulations and quantifying production‐induced stresses which may lead to rock failure. Current methods for estimating stress anisotropy from acoustic anisotropy rely on third‐order elasticity, which ignores rock microstructure and gives elastic moduli that vary linearly with strain. Elastic stiffnesses in sandstones vary non‐linearly with stress. Using P‐ and S‐wave velocities measured on Gulf of Mexico sandstones, this non‐linearity is found to be consistent with a micromechanical model in which the discontinuities are represented by stress‐dependent normal and shear compliances. Stress‐induced anisotropy increases with increasing stress anisotropy at small stress but then decreases at larger stresses as the discontinuities close and their compliance decreases. When the ratio of normal‐to‐shear compliance of the discontinuities is unity, the stress‐induced anisotropy is elliptical, but for values different from unity, the stress‐induced anisotropy becomes anelliptic. Although vertical stress can be obtained by integrating the formation's bulk density from the surface to the depth of interest, and minimum horizontal stress can be estimated using leak‐off tests or hydraulic fracture data, maximum horizontal stress is more difficult to estimate. Maximum horizontal stress is overpredicted based on third‐order elasticity using measured shear moduli, with estimates of pore pressure, vertical stress and minimum horizontal stress as input. The non‐linear response of grain contacts and microcracks to stress must be considered to improve such estimates.

Carotid Intima-Media Thickness in Children with Chronic Kidney Disease as an Early Predictor of Cardiovascular Diseases

Aim: Cardiovascular problems are very common in children with chronic kidney disease (CKD). To examine early cardiovascular risk factors, notably carotid intima-media thickness (CIMT) and pulse wave velocity (PWV). Material and Method: Case-control study was conducted in the Department of Pediatric Nephrology Sindh Institute of Urology and Transplantation Karachi from 1stFebruary 2023 to 31st July 2023. Forty two children were enrolled. CIMT and PWV were measured using ultrasonography and pulse wave analysis respectively. The following clinical parameters were also assessed: blood pressure, age, gender, etiology, duration of chronic kidney disease (CKD), estimated glomerular filtration rate (eGFR), serum albumin, calcium-phosphate product, and intact parathyroid hormone (PTH), and vitamin D levels. Results: The average age was 10.2±3.6 years, with a higher proportion of boys in the cases group (69% versus 47.6%, p-value 0.04). Most patients had normal blood pressure (78.6%), and congenital anomalies were the most common CKD etiology (57.1%). Median eGFR was 30.5 ml/min/1.73 m2, with stages 3 and 4 CKD most prevalent. Serum albumin was normal (mean 4.45±0.68), but some cases had a high calcium-phosphate product (7%) and low vitamin D levels (52%). CIMT and PWV did not differ significantly between cases and controls. Echocardiography revealed mild cardiac abnormalities in some cases. Practical implication: Some patients showed minor left ventricular expansion, while others had mildly depressed GLS and decreased LVEF. Further research should focus on longitudinal studies and explore new biomarkers for early cardiovascular risk detection. Conclusion: The various clinical characteristics such as blood pressure, mineral and bone diseases, and cardiac abnormalities are common in children with chronic kidney diseases. There were no significant changes in carotid intima-media thickness and pulse wave velocity between the cases and controls. Keywords: Chronic kidney disease, Carotid intima-media thickness, Cardiovascular disease, Pulse wave velocity

Structure and elasticity of CaC2O5 suggests carbonate contribution to the seismic anomalies of Earth’s mantle

Knowledge of carbonate compounds under high pressure inside Earth is key to understanding the internal structure of the Earth, the deep carbon cycle and major geological events. Here we use first-principles simulations to calculate the structure and elasticity of CaC2O5-minerals with different symmetries under high pressure. Our calculations show that CaC2O5-minerals represent a group of low-density low-seismic-wave velocity mantle minerals. Changes in seismic wave velocity caused by the phase transformation of CaC2O5-Cc to CaC2O5-I4¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\bar{4}$$\\end{document}2d (CaC2O5-C2-l) agree with wave velocity discontinuity at a depth of 660 km in the mantle transition zone. Moreover, when CaC2O5-Fdd2 transforms into CaC2O5-C2 under 70 GPa, its shear wave velocity decreases by 7.4%, and its density increases by 5.8%, which is consistent with the characteristics of large low-shear-velocity provinces (LLSVPs). Furthermore, the shear wave velocity of CaC2O5-I4¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\bar{4}$$\\end{document}2d is very similar to that of cubic Ca-perovskite, which is one of the main constituents of the previously detected LLSVPs. Therefore, we propose that CaC2O5 and its high-pressure polymorphs may be a main component of LLSVPs.

The effects of internal erosion on granular soils used in transport embankments

The flooding of embankments used for rail and other infrastructure has the potential to cause lasting weakening of slopes via the movement of fine particles induced by seepage. In laboratory experiments, internal erosion was induced in granular soil samples, with properties consistent with those used to construct transportation embankments, to assess how particle migration through, and out of, samples caused shear wave velocity, strength, stiffness and permeability changes. Shear wave velocity changes, measured using horizontal bender elements, of up to 19 % were observed following fine particle removal of up to 1 % of initial sample mass. Shear wave velocity change was found to be an indicator for identifying the development of permeability change during seepage-induced particle migration. Median measured permeability changes were +5 % and −34 % for samples containing 15 % and 30 % fines, respectively. The largest directly observed permeability and shear wave velocity changes occurred during the initial stages of seepage. Negative correlation was observed between mass of material removed from samples and peak friction angle. Following seepage, soils displayed a dual stiffness behaviour. Stiffness and strength changes were attributed to redistribution of fine particles and opening of pore spaces. Our results have implications for the monitoring of earthworks affected by flooding and seepage as the associated redistribution of fine particles may lead to large changes in slope properties.

Physical mechanism of the variation of longitudinal wave velocity with porosity in seafloor sediments

In order to reveal the response mechanism of longitudinal wave velocity and related parameters, through the statistical analysis of the measurement data of seafloor sediments, it is found that there is a minimum value of the change of longitudinal wave velocity with porosity of seafloor sediments. The minimum values of the empirical formula for the change of longitudinal wave velocity with porosity of sediments in different sea areas and their critical porosity values are uniformly analyzed. The calculation shows that the minimum variation range of longitudinal wave velocity with porosity of sediments in different sea areas is between 1468.59 and 1520.22 m/s, and the corresponding critical porosity value changes between 0.69 and 0.88. The analysis shows that the empirical formulas of different scholars belong to the unified mathematical expression derived from acoustic theory. The study shows that the essential reason for the formation of the minimum of longitudinal wave velocity in seafloor sediment is that the coupling of sediment grains affects the propagation of longitudinal wave. It is further revealed that the physical mechanism of the change of longitudinal wave velocity is that the change of contact or suspension state of seafloor sediment grains in seawater affects the elastic stress-strain relations of sediments.

Surface Acoustic Waves (SAW) Sensors: Tone-Burst Sensing for Lab-on-a-Chip Devices.

The article presents the design concept of a surface acoustic wave (SAW)-based lab-on-a-chip sensor with multifrequency and multidirectional sensitivity. The conventional SAW sensors use delay lines that suffer from multiple signal losses such as insertion, reflection, transmission losses, etc. Most delay lines are designed to transmit and receive continuous signal at a fixed frequency. Thus, the delay lines are limited to only a few features, like frequency shift and change in wave velocity, during the signal analysis. These facts lead to limited sensitivity and a lack of opportunity to utilize the multi-directional variability of the sensing platform at different frequencies. Motivated by these facts, a guided wave sensing platform that utilizes simultaneous tone burst-based excitation in multiple directions is proposed in this article. The design incorporates a five-count tone burst signal for the omnidirectional actuation. This helps the acquisition of sensitive long part of the coda wave (CW) signals from multiple directions, which is hypothesized to enhance sensitivity through improved signal analysis. In this article, the design methodology and implementation of unique tone burst interdigitated electrodes (TB-IDT) are presented. Sensing using TB-IDT enables accessing multiple frequencies simultaneously. This results in a wider frequency spectrum and allows better scope for the detection of different target analytes. The novel design process utilized guided wave analysis of the substrate, and selective directional focused interdigitated electrodes (F-IDT) were implemented. The article demonstrates computational simulation along with experimental results with validation of multifrequency and multidirectional sensing capability.

Longitudinal assessment of liver stiffness using ARFI technique does not support increased risk of fibrosis in rheumatoid arthritis patients on methotrexate.

To assess the liver stiffness in patients with rheumatoid arthritis treated with methotrexate monotherapy using non-invasive, ultrasound-based elastography (acoustic radiation force impulse (ARFI) imaging) in a longitudinal approach. In total, 23 MTX-naive patients were longitudinally assessed using acoustic radiation force impulse (ARFI) imaging. Baseline assessments were carried out between July 2018 and April 2019, and the follow-up evaluations took place after an average of 2.6years. The main outcome variable was the mean shear wave velocity as measured by the ARFI method. It was calculated from 10 valid ARFI measurements for each patient. Inferential statistical analyses (within-group comparisons) were performed using t-tests for dependent samples or suitable nonparametric procedures. The main finding was that observed ARFI shear wave velocities did not increase during the observation period. In fact, this parameter decreased over time from 1.07m/s (SD = 0.23) at baseline without MTX exposure to 0.97m/s (SD = 0.16) at follow-up after a mean of 2.6years (P = 0.013). Moreover, the magnitude of the change in shear wave velocity could not be predicted by indicators of inflammation or disease activity, BMI, age, sex or NSAR intake (corresponding regression analysis: corrected R2 = 0.344; P = 0.296). No increased risk of liver fibrosis was found in RA patients treated with MTX monotherapy during observation period.

The Impact of Finerenone on Changes in Pulse Wave Velocity, Arterial Pressure and Heart Related Deaths in Hemodialysis Patients—Study Perspective

The Impact of Finerenone on Changes in Pulse Wave Velocity, Arterial Pressure and Heart Related Deaths in Hemodialysis Patients—Study Perspective

Effects of low-pressure Valsalva maneuver on changes in cerebral arterial stiffness and pulse wave velocity.

The Valsalva maneuver (VM), commonly used to assess cardiovascular and autonomic nervous system functions, can induce changes in hemodynamic function that may affect cerebral vascular functionality, such as arterial elasticity. This study aimed to investigate the effects of low-pressure VM on cerebral arterial stiffness and cerebral vascular dynamics. Thirty-one healthy young participants (average age 21.58±1.72 years) were recruited for this study. These participants were instructed to maintain an expiratory pressure of 30-35 mmHg for 15 seconds. We measured the vasoconstriction and vasodilation diameters (VCD and VDD) of the common carotid artery (CCA), as well as systolic and diastolic blood pressures (SBP and DBP), before and after VM (PRE_VM and POST_VM). Additionally, we assessed mean arterial pressure (MAP), pulse pressure (PP), pulse wave velocity (PWV), and arterial stiffness. Our findings revealed significant increases in both the VCD and VDD of the CCA (2.15%, p = 0.039 and 4.55%, p<0.001, respectively), MAP (1.67%, p = 0.049), and DBP (1.10%, p = 0.029) following low-pressure VM. SBP showed an increasing trend, but this was not statistically significant (p = 0.108). Interestingly, we observed significant decreases in arterial stiffness and PWV in POST_VM when comparing with PRE_VM (p<0.001 and p<0.001, respectively). In conclusion, our study demonstrated the effectiveness of low-pressure VM in reducing the PWV and stiffness of the CCA. This suggests that low-pressure VM can be a simple and cost-effective method to reduce cerebrovascular stiffness in a brief interval, without the need for specific environmental conditions.

Evaluation of the coefficient of lateral stress at rest of granular materials under repetitive loading conditions

Although the internal stress state of soils can be affected by repetitive loading, there are few studies evaluating the lateral stress (or K0) of soils under repetitive loading. This study investigates the changes in K0 and directional shear wave velocity (Vs) in samples of two granular materials with different particle shapes during repetitive loading. A modified oedometer cell equipped with bender elements and a diaphragm transducer was developed to measure the variations in the lateral stress and the shear wave velocity, under repetitive loading on the loading and unloading paths. The study produced the following results: (1) Repetitive loading on the loading path resulted in an increase in the K0 of test samples as a function of cyclic loading number (i), and (2) Repetitive loading on the unloading path resulted in a decrease in K0 according to i. The shear wave velocity ratio (i.e. Vs(HH)/Vs(VH), where the first and second letters in parentheses corresponds to the directions of wave propagation and particle motion, respectively, and V and H corresponds to the vertical and horizontal directions, respectively) according to i supports the experimental observations of this study. However, when the tested material was in lightly over-consolidated state, there was an increase in K0 during repetitive loading, indicating that it was the initial K0, rather than the loading path, which is responsible for the change in K0. The power model can capture the variation in the K0 of samples according to i. Notably, the K0 = 1 line acts as the boundary between the increase and decrease in K0 under repetitive loading.

Comparing the stretching technique and the wavelet cross-spectrum technique for measuring stress-induced wave-velocity changes in concrete

Coda wave interferometry (CWI) holds promise as a technique for concrete stress monitoring. This is because the coda, which consists of multiply scattered arrivals, is the result of propagation through the medium over large distances. As such, it is sensitive to both minute structural changes and small velocity changes in that medium. Previous studies focusing on concrete have predominantly utilized the time-domain-based stretching technique to measure travel-time changes. There is, however, a lack of consensus on how to quantify these changes effectively. In this study, we conduct a systematic comparison between two techniques, namely the stretching technique and the wavelet cross-spectrum (WCS) technique, for measuring stress-induced velocity changes in a cylindrical concrete sample. Our comparison focuses on two key aspects: (i) stability against cycle skipping and (ii) consistency in retrieving velocity changes. Experimental results reveal that both the WCS technique and the stretching technique yield consistent velocity changes. In terms of stability, it is challenging to determine which technique performs better, due to differences in the mechanisms triggering cycle skipping. However, when considering waves with frequencies ranging from 50 kHz to 80 kHz, both techniques exhibit comparable performance. Based on our findings, we offer the following recommendations for utilizing these CWI techniques in concrete stress monitoring:For the stretching technique, selecting the time window length based on the wave frequency and the expected magnitude of velocity change.For the WCS technique, operating it in the frequency band where spectral decomposition shows sufficiently high energy in the signal and can accommodate the expected magnitude of velocity change.

Leveraging doppler ultrasound imaging to measure pulse wave velocity changes in a mouse model of arterial stiffening to elucidate molecular pathways underlying cerebral damage

AbstractBackgroundThe highly vascularized brain is particularly vulnerable to changes in pulsatility of blood flow. With age, elastin in arteries breaks down and is replaced by collagen, making arteries less compliant and resulting in arterial stiffening. Stiffening alters pulsatility, which can be measured by pulse wave velocity (PWV), and damages small capillary beds and the neurovascular unit (NVU). The NVU is essential for proper delivery of oxygen and nutrients to the brain. Human studies have demonstrated associations between increased arterial stiffness and biomarkers of Alzheimer’s disease (AD) and neurodegeneration. We adapted a doppler ultrasound imaging method previously only used in rats to measure PWV in a mouse model of arterial stiffening to advance our understanding of the molecular underpinnings of AD and neurodegeneration.Method7‐month‐old, C57BL/6, male and female mice underwent a carotid calcification surgery, where the carotid artery was exposed to 0.3 mol/L CaCl2 (or saline as a control) for 20 minutes. PWV was measured using doppler ultrasound imaging before and after surgery. Two weeks post‐surgery, mice underwent behavioral testing, including locomotor activity, elevated zero maze, Barnes maze, and nest building. Collagen, calcium, and elastin levels in the carotid artery were determined 4 weeks post‐surgery by immunohistochemistry.ResultPreliminary results demonstrate the carotid calcification surgery successfully increased PWV in mice three weeks post‐surgery. Surgery did not inhibit behavioral task performances two weeks post‐operative. Additional data collection is underway applying this method in two transgenic AD mouse models, APP/PSEN1 and P301S, which will include behavioral testing and histological assessment of NVU components, specifically endothelial cells (CD31/PECAM), pericytes (PDGRFb), and astrocytes (GFAP) in the hippocampus.ConclusionElucidating a clear molecular link between increased arterial stiffness and cognition is essential to understanding how age‐related changes in systemic blood flow may influence AD pathology and neurodegeneration. Our preliminary results demonstrate that doppler ultrasound imaging, previously only used in rats, can be applied in mice as a reliable measurement of PWV. We will leverage this model to test the hypothesis that increased PWV is associated with worse spatial learning and memory, impaired functioning of the NVU, and increased AD pathology.

The effect of resveratrol on aortic growth and function in patients with marfan syndrome

Abstract Background Patients with Marfan syndrome (MFS) have an increased risk of life-threatening aortic complications, mostly preceded by aortic dilatation. Resveratrol, a dietary supplement that intervenes in cellular metabolism has been shown to reduce aortic dilatation rate in a rodent study (1). Purpose To investigate if treatment with Resveratrol reduces aortic dilatation rate in patients with MFS. Methods In this investigator-initiated, prospective, pre-post observational, multicenter trial, we analysed Resveratrol treatment in adults with MFS. Primary endpoint was the change in aortic dilatation rate at five predetermined locations along the thoracic aorta following the daily intake of 500 mg Resveratrol for one year. Aortic dilatation rate was calculated using diastolic Magnetic Resonance Imaging (MRI) aorta diameters acquired at three time points: the most recent MRI examination available prior to inclusion and two Dixon 3D examinations on a 3 Tesla MRI system acquired at baseline and after one year Resveratrol administration. Additionally, we quantified and investigated regional changes in aortic hemodynamics (wall shear stress (WSS), flow velocity and pulse wave velocity (PWV)) determined by 4D-flow MRI. Results A total of 57 participants, mean age of 37 ± 9 years, of which 28 males (49%) were included in the study. Twenty-six (46%) had undergone aortic root replacement prior to the study. All aortic dimensions remained stable after 1.2 ± 0.3 years follow-up. A significant decrease in growth rate (mm/year) in the ascending aorta was observed during the trial compared to pre-trial, from 0.54 (IQR: 0.09–1.39) to 0.00 (IQR: -0.99–0.67), p=0.004. Global PWV and regional mean WSS and velocity did not change after one year of Resveratrol use. PWV (m/s) was significantly higher for patients with a history of aortic root surgery (9.83 ± 1.8 versus 8.42 ± 1.91, p=0.034). Additionally, using Spearman’s ρ correlation coefficient, a positive correlation between PWV and age was found; r=0.452, p=0.003. Conclusion In adult patients with MFS, Resveratrol treatment shows promising results towards stabilizing aortic growth rate after 1.2 year follow up, without major changes in aorta hemodynamics. These findings may warrant a subsequent larger study with a longer follow-up period.RESVcue study summary figure

Evaluating changes in shear wave velocity due to blast-induced liquefaction

Blast liquefaction tests were performed in Christchurch, New Zealand in an area that experienced extensive liquefaction during the 2010–2011 Canterbury Earthquake Sequence. To evaluate the changes in shear wave velocity (VS) of the soil profile in the vicinity of the blasting, multi-channel analysis of surface waves (MASW) testing was performed before the blast, immediately following the blast (within 0.5 h), 4 h post-blast, and 24 h post-blast. Three different array setups with varying lengths and number of geophones were analyzed to study the effect of array length on the ability of MASW to capture changes in VS within the blast area. Results of the study show that array length can have a significant effect on the measured changes in VS immediately following blasting due to averaging of the properties inside and outside of the area where blasting induced liquefaction developed; however, these changes decrease at 24 h. Full recovery of pre-blast VS was not observed for all layers at 24 h post-blast. This study provides data for measurements of VS rapidly following liquefaction, which are sparse in the literature.

The Impact of Mineralocorticoid Receptor Blockers on Changes in Pulse Wave Velocity, Arterial Pressure and Heart Related Deaths in Hemodialysis Patients

The Impact of Mineralocorticoid Receptor Blockers on Changes in Pulse Wave Velocity, Arterial Pressure and Heart Related Deaths in Hemodialysis Patients

Wave Velocities and Poisson Ratio in a Loose Sandy Martian Regolith Simulant Under Low Stresses: 1. Laboratory Investigation

AbstractWave velocity measurements were performed on Fontainebleau sand samples used as a Martian regolith simulant to investigate the elastic properties of the surface material at the InSight landing site on Mars (Elysium Planitia). Loose samples (density 1.4 Mg/m3, density index 6%) were prepared by using the pluviation method to mimic the low regolith density at the InSight landing site. A novel device derived from triaxial testing was designed to measure wave velocities at low stresses along a horizontal cylindrical specimen. Four tests were made, in which the confining stress was applied by applying a vacuum between 1 and 80 kPa. Wave velocities were measured by using bender elements under stresses as low as 1.75 kPa, a very low value compared to the standard stress ranges generally considered in terrestrial geotechnics (&gt;10 kPa). The changes in compression and shear wave velocities obey a standard power law, with two slightly different exponents for Vp and Vs, indicating a not perfectly elastic behavior. Data showed greater variability below 5 kPa, indicating some limitations of the bender element technique in this range. A slight decrease in Poisson ratio was detected below 5 kPa, which certainly deserves more investigation. This investigation is useful to better analyze the data of the InSight mission, both in terms of wave propagation at the surface and to interpret some in situ elastic tests carried out with the scoop. These data are interpreted in the light of a granular contact mechanics theory in a companion paper.

Experimental study on the influence of ultrasonic excitation duration on the pore and fracture structure and permeability of coal body

The study aims to explore the effect of ultrasonic duration on the pore structure and seepage characteristics of coal. Herein, we adopted a self-developed ultrasonic excitation experiment system using low-field nuclear magnetic resonance (NMR) technology and NM-4B non-metallic ultrasonic wave velocity detector. The study investigated NMR relaxation time T2 patterns and the number of pores of each size, internal structural damage, and seepage characteristics of the coal body before and after ultrasonic fracturing. Based on the Warren-Root model, the permeability model of coal under ultrasonic fracturing was established, revealing the changing law of ultrasonic fracturing at different times on the change of pore scale, connectivity, and nuclear magnetic permeability of the coal body. The mechanism of ultrasonic fractured coal body evolution at different times was clarified. The results showed that the ultrasonic fracturing at different times improved the number and volume of all size pores in the coal body, expanded primary fractures, and developed newborn fractures. The rate of change in pore size, porosity, wave velocity, and coal permeability had a linear relationship with the fracturing time. The growth rate of seepage pore volume proportion was positively correlated to the decreased rate of adsorption pore volume proportion. The fracturing duration leads to the interconnection of micropores within the coal body, forming medium and large pore fractures. This transformation between pores and fractures enhances the pore structure and seepage characteristics of the coal body. The coal rock permeability model can be used to calculate the permeability of a coal body, which follows the same change law as nuclear magnetic permeability. When evaluating the index using absolute and relative errors, the range of relative error is 0.97%–7.91%. The error variation range is small, indicating that the established model can effectively reflect the change law of porosity and permeability of the coal body responding to ultrasonic fracturing. The ultrasonic fracturing rendered the ultrasonic cavitation takes micropores as fracturing units, developed pores of all sizes, connected closed pores, increased free fluid space proportion, and improved the coal permeability.

Analysis of Heart Pulse Transmission Parameters Determined from Multi-Channel PPG Signals Acquired by a Wearable Optical Sensor

Abstract The article describes the development and testing of a special prototype wearable device consisting of three optical photoplethysmography (PPG) sensors. The functionality of the developed triple PPG sensor was tested under normal laboratory conditions and in a running magnetic resonance imaging (MRI) scanner working with a low magnetic field. The results of the first measurements under normal laboratory conditions show that the obtained mutual positions of systolic/diastolic blood pressure values and heart pulse transmission parameters determined from the PPG waves can be fitted by a line segment with a sufficiently high slope. Measurement experiments inside the open-air MRI tomograph show the practical influence of vibrations and acoustic noise on the cardiac system of the examined persons, which was confirmed by a slight increase in the heart pulse rate and changes in pulse transmission time and pulse wave velocity. We plan to perform further measurements inside the whole-body MRI device producing more intensive vibrations and noise with expected higher stress impact on an exposed person.