3D Strain Research Articles

Subchondral bone fatigue injury in the parasagittal condylar grooves of the third metacarpal bone in thoroughbred racehorses elevates site-specific strain concentration

Condylar stress fracture of the distal end of the third metacarpal/metatarsal (MC3/MT3) bones is a major cause of Thoroughbred racehorse injury and euthanasia worldwide. Functional adaptation to exercise and fatigue damage lead to structural changes in the subchondral bone that include increased modeling (resulting in sclerotic bone tissue) and targeted remodeling repair (resulting in focal resorption spaces in the parasagittal groove). Whether these focal structural changes, as detectable by standing computed tomography (sCT), lead to elevated strain at the common site of condylar stress fracture has not been demonstrated. Therefore, the goal of the present study was to compare full-field three-dimensional (3D) strain on the distopalmar aspect of MC3 bone specimens with and without focal subchondral bone injury (SBI). Thirteen forelimb specimens were collected from racing Thoroughbreds for mechanical testing ex vivo and underwent sCT. Subsequently, full-field displacement and strain at the joint surface were determined using stereo digital image correlation. Strain concentration was observed in the parasagittal groove (PSG) of the loaded condyles, and those with SBI in the PSG showed higher strain rates in this region than control bones. PSG strain rate in condyles with PSG SBI was more sensitive to CT density distribution in comparison with condyles with no sCT-detectable injury. Findings from this study help to interpret structural changes in the subchondral bone due to fatigue damage and to assess risk of incipient stress fracture in a patient-specific manner.

Tensile damage evolution and mechanical behaviour of SiCf/SiC mini-composites through 4D in-situ micro-CT and data-driven modelling

Damage evolution of SiCf/SiC ceramic matrix mini-composites (CMMCs) was characterised by using a 4D in-situ micro-computed tomography (CT) tensile test and digital volume correlation (DVC) technique. Additionally, a CT damage data-driven shear lag model was developed to predict its tensile stress-strain response. A 4D in-situ X-ray CT tensile test of a unidirectional SiCf/SiC mini-composite was first carried out. Then two ad-hoc deep-learning image segmentation models were developed to automatically identify its microstructure and damages induced by tension, respectively. Damage evolution was quantitively characterised by visualising the initiation and propagation of matrix cracks in three-dimensions (3D). A two-step approach was employed to evaluate its 3D internal strain distributions at various loading levels, which further revealed strain concentrations and helped establishing the tensile stress-strain response of the CMMCs. It was observed that transverse cracking is the predominant damage mode, and the average crack opening displacement increases with loading. A high-fidelity X-ray CT data-driven shear lag model was developed, incorporating inputs of transverse matrix crack spacing calculated by the 4D in-situ CT test data. The predicted stress-strain response showed a good correlation with the experimental results.

A three-dimensional left atrial motion estimation from retrospective gated computed tomography: application in heart failure patients with atrial fibrillation.

A reduced left atrial (LA) strain correlates with the presence of atrial fibrillation (AF). Conventional atrial strain analysis uses two-dimensional (2D) imaging, which is, however, limited by atrial foreshortening and an underestimation of through-plane motion. Retrospective gated computed tomography (RGCT) produces high-fidelity three-dimensional (3D) images of the cardiac anatomy throughout the cardiac cycle that can be used for estimating 3D mechanics. Its feasibility for LA strain measurement, however, is understudied. The aim of this study is to develop and apply a novel workflow to estimate 3D LA motion and calculate the strain from RGCT imaging. The utility of global and regional strains to separate heart failure in patients with reduced ejection fraction (HFrEF) with and without AF is investigated. A cohort of 30 HFrEF patients with (n = 9) and without (n = 21) AF underwent RGCT prior to cardiac resynchronisation therapy. The temporal sparse free form deformation image registration method was optimised for LA feature tracking in RGCT images and used to estimate 3D LA endocardial motion. The area and fibre reservoir strains were calculated over the LA body. Universal atrial coordinates and a human atrial fibre atlas enabled the regional strain calculation and the fibre strain calculation along the local myofibre orientation, respectively. It was found that global reservoir strains were significantly reduced in the HFrEF + AF group patients compared with the HFrEF-only group patients (area strain: 11.2 ± 4.8% vs. 25.3 ± 12.6%, P = 0.001; fibre strain: 4.5 ± 2.0% vs. 15.2 ± 8.8%, P = 0.001), with HFrEF + AF patients having a greater regional reservoir strain dyssynchrony. All regional reservoir strains were reduced in the HFrEF + AF patient group, in whom the inferior wall strains exhibited the most significant differences. The global reservoir fibre strain and LA volume + posterior wall reservoir fibre strain exceeded LA volume alone and 2D global longitudinal strain (GLS) for AF classification (area-under-the-curve: global reservoir fibre strain: 0.94 ± 0.02, LA volume + posterior wall reservoir fibre strain: 0.95 ± 0.02, LA volume: 0.89 ± 0.03, 2D GLS: 0.90 ± 0.03). RGCT enables 3D LA motion estimation and strain calculation that outperforms 2D strain metrics and LA enlargement for AF classification. Differences in regional LA strain could reflect regional myocardial properties such as atrial fibrosis burden.

Orientation Dependency of 3D printed SHCC at increasing length scale

In the first part of this study, the inclination-dependent effects on a single fibre embedded in 3D printable strain hardening cementitious composite are studied. Two distinct failure modes (i.e., slipping rupture and complete pull-out) were found in the experimental results. Based on these failure modes two separate slip-hardening factors have been determined and analysed with an analytical fibre pull-out model. The second part of the study focused on the influence of multiple fibres with varying inclination angles on single- and multiple-cracking specimens. These tests have been performed for specimens that were casted and printed, to analyse the effect on ductility due to the extrusion process. Three orthogonal directions were examined within the printed specimens during testing. The amount of energy dissipated during the crack opening is strongly orientation-dependent for 3DP-SHCC and does not significantly increase in the main printing direction compared to casted SHCC. Furthermore, the orientation-dependent ductility is evaluated in bending with the use of a 4PB test. Allowing multiple layers of fibre-reinforced material to become active at the same time. The strain hardening effect found in a single crack is amplified by the material’s capability to develop multiple cracks, ultimately leading to a significant increase in its impact on engineering applications related to bending.

3D microstructural and strain evolution during the early stages of tensile deformation

Dislocation patterning and self-organization during plastic deformation are associated with work hardening, but the exact mechanisms remain elusive. This is partly because studies of the structure and local strain during the initial stages of plastic deformation are a challenge. For this reason, literature data typically cover strains from 0.05-0.1 and higher. Here we use Dark Field X-ray Microscopy to generate 3D maps of embedded 350×900×72μm3 volumes within three pure Al single crystals. Tensile deformation was applied to true strains of 0.6%, 1.7%, and 3.5% along the [10 13 −10] direction. Orientation maps revealed the existence of two distinct types of planar dislocation boundaries both at 0.6% and 1.7% but no systematic patterning. At 3.5%, these boundaries have evolved into a well-defined checkerboard pattern, characteristic of Geometrically Necessary Boundaries, GNBs. The crystallographic alignment of the GNBs match that in polycrystals for grains of similar orientation. The GNB spacing measured perpendicular to the planesis ≈6μm and the misorientation ≈0.2°, in fair agreement with literature data for higher strains. By contrast to the sharp boundaries observed at higher strains, the boundaries are associated with a sinusoidal orientation gradient, showing that they are not yet fully formed. Maps of the elastic strain along the (111) direction exhibit strain variations of ±0.0002 with an average domain size of 3μm.

Construction of prokaryotic system for expression of porcine circovirus type 2 ORF-2 gene fragment

Porcine circovirus-associated diseases (PCVDs) are among the most significant challenges for pig farming in developed countries. Porcine circovirus type 2 (PCV-2) is considered the main etiological agent of postweaning multisystemic wasting syndrome in piglets. Mass PCVD occurrence has been reported in most regions of the world, that results in serious economic consequences. Optimal PCVD prevention is known to be achieved through a set of veterinary and sanitary measures in combination with vaccination. High evolutionary virus variability facilitating new genotype and strain emergence requires development of new candidate recombinant vaccines against PCV-2 infection. The study was aimed at construction of prokaryotic system for PCV-2 ORF-2 gene fragment expression and its functionality assessment. A genetic insert constructed from the most immunogenic type-specific PCV-2 epitopes based on genotype 2a, 2b, 2d strain and isolate consensus sequence was cloned into the expression vector pET-22b(+) that was incorporated into the Escherichia coli strain Rosetta 2(DE3). The transformants were selected based on the marker gene of ampicillin resistance on a selective medium. Target gene expression was induced by adding of isopropyl-β-D-1-thiogalactopyranoside at different concentrations. As a result, Escherichia coli Rosetta 2(DE3)/pET-22b-ORF-2 strain, a producer of capsid protein fragment (92–233 amino acid residues), was constructed. It was found that in the presence of 1 mM isopropyl-β-D-1-thiogalactopyranoside, the expression level of soluble truncated rCap was 35–40 mg/L 6 hours after induction. The expression product was tested for its specificity with indirect ELISA using whole-virion PCV-2-hyperimmunized porcine serum. It was shown that the positivity coefficient of producer strain cell lysates averaged to 4.34 (p < 0.005). The recombinant rCap protein is suitable for serological diagnosis and is also of interest as a vaccine component, which is the goal of our further studies.

Three-dimensional surface strain sensor based on PDMS/LIG composite film with adjustable electromechanical performance

Flexible strain sensors play a crucial role in health monitoring, smart wearable devices, and human–machine interaction. Three-dimensional surface evaluation methods for strain sensors offer advantages by being closer to actual strain, featuring a larger working range, and being more suitable for multidirectional strain. In this study, a three-dimensional (3D) surface strain sensor based on polydimethylsiloxane/laser-induced graphene (PDMS/LIG) composite films has been developed. The electromechanical properties of this sensor, encompassing 3D strain range and sensitivity, can be adjusted by manipulating laser parameters and LIG patterns. The key to attaining these specific characteristics lies in the intentional design of crack types and orientations on the sensor's surface. Remarkably, the line-vertical (LV) sensor exhibits outstanding sensitivity with a GF of 211.3. The line-parallel (LP) sensor achieves a GF of 115.1. Additionally, it demonstrates a stretching range of 25% and maintains stable performance over an extensive number of strain/release test cycles (more than 3000 cycles). With these advantages, the 3D strain sensor can not only be applied in human activity monitoring but also monitoring pressure within microchannels in microfluidic chips, suggesting promising applications in the health and medical fields.

Material representativeness of a polymer matrix doped with nanoparticles as the random speckle pattern for digital volume correlation of fibre-reinforced composites

Combining tomographic imaging with digital volume correlation allows in-situ 3D strain mapping, leading to a quantitative assessment of damage mechanisms and associated material properties in structural materials. Being based on pattern recognition, digital volume correlation is well-suited for materials with intrinsic and stable microstructural heterogeneity, such as certain biological tissues. Unfortunately, conventional polymers and fibre-reinforced polymer composites lack the required heterogeneity. Recently, solutions like doping the polymers with particles have been explored to overcome this limitation. The particles embedded in the polymer matrix provide a random, volumetric speckle pattern, acting as displacement trackers for the digital volume correlation algorithm. However, the particles might influence the mechanical and rheological behaviour of the polymer, which is detrimental in investigations of the composite material properties. This paper investigates the mechanical, mechanistic, and rheological representativeness of an epoxy doped with two types of sub-micrometre particles optimised for digital volume correlation. Since particle dispersion is considered a key driver for representativeness, we simultaneously quantitatively assess the dispersion by combining scanning electron microscopy and X-ray computed tomography.

Self-assembly of Co/Pt stripes with current-induced domain wall motion towards 3D racetrack devices

Modification of the magnetic properties under the induced strain and curvature is a promising avenue to build three-dimensional magnetic devices, based on the domain wall motion. So far, most of the studies with 3D magnetic structures were performed in the helixes and nanowires, mainly with stationary domain walls. In this study, we demonstrate the impact of 3D geometry, strain and curvature on the current-induced domain wall motion and spin-orbital torque efficiency in the heterostructure, realized via a self-assembly rolling technique on a polymeric platform. We introduce a complete 3D memory unit with write, read and store functionality, all based on the field-free domain wall motion. Additionally, we conducted a comparative analysis between 2D and 3D structures, particularly addressing the influence of heat during the electric current pulse sequences. Finally, we demonstrated a remarkable increase of 30% in spin-torque efficiency in 3D configuration.

Changes in subclinical cardiac abnormalities 1 Year after recovering from COVID-19 in patients without clinical cardiac findings

AimTo evaluate the subclinical cardiac involvement in COVID-19 patients without clinical cardiac evidence using cardiac MR imaging. Material and methodsParticipants recovered from COVID-19 without cardiac symptoms and no cardiovascular medical history were enrolled in a prospective cohort study. They underwent baseline cardiac MR and follow-up cardiac MR > 300 days after discharge (n = 20). The study also included healthy controls (n = 20). Extracellular volume fraction (ECV), native T1, and 2D strain data were assessed and compared. ResultsThe ECV values of participants at baseline [30.0% (28.3%–32.5%)] and at follow-up [31.0% (28.0%–32.8%)] were increased compared to the healthy control group [27.0% (25.3%–28.0%)] (both p < 0.001). However, the ECV increase from baseline cardiac MR to follow-up cardiac MR was not significant (p = 0.378). There was a statistically significant difference in global native T1 between baseline [1140 (1108.3–1192.0) ms] and follow-up [1176.0 (1113.0–1206.3) ms] (p = 0.016). However, no native T1 difference was found between the healthy controls [1160.7 (1119.6–1195.4) ms] and the baseline (p = 0.394) or follow-up group (p = 0.168). The global T2 was 41(40–42) ms at follow-up which was within the normal range. In addition, We found a recovery in 2D GLS among COVID-19 participants between baseline and follow-up [-12.4(-11.7 to −14.3)% vs. −17.2(-16.2 to −18.3)%; p＜0.001]. ConclusionUsing cardiac MR myocardial tissue and strain imaging parameters, 35% of people without cardiac symptoms or clinical evidence of myocardial injury still had subclinical myocardial tissue characteristic abnormalities at 300 days, but 2D GLS had recovered.

Evaluation of the Relationship Between Vitamin D Deficiency and Subclinical Cardiac Dysfunction Using 2D/3D Strain Echocardiography in Healthy People.

Vitamin D deficiency has a high prevalence in the population and is highly associated with cardiovascular diseases. The aim of this study was to evaluate subclinical left ventricular (LV) function using strain analysis in healthy individuals with vitamin D deficiency. 113 healthy volunteers were enrolled in the study (age, 44.1±7 yrs, 34 male). All volunteers underwent two-dimensional (2D) and three-dimensional (3D) speckle tracking echocardiography after conventional echocardiographic evaluation. The subjects were divided into two groups according to their vitamin D concentrations. 61 subjects with vitamin D less than 20 ng / ml were included in the vitamin D deficiency group. The baseline clinical characteristics, laboratory measurements, echocardiographic data, including 2D and 3D global longitudinal strain (GLS) values, were compared between the groups. The 2D GLS values of the subjects with vitamin D deficiency were lower (mathematically less negative) than subjects with normal vitamin D (-16.1±3.4 vs -19.3±4.2, p&lt;0.001). Similarly, the 3D GLS results were lower in subjects with vitamin D deficiency (-18.3±5.2 vs -24.1±6.9, p&lt;0.001). A significant correlation was detected between the vitamin D concentrations and the 2D and 3D GLS measurements. (r=0.765 and r=0.628, respectively, p&lt;0.001). Vitamin D was found to be an independent predictor of impaired 2D and 3D LV GLS (p=0.031, p=0.023, respectively). Subclinical LV dysfunction in healthy individuals with vitamin D deficiency was demonstrated by 3D and 2D strain analysis. Due to potential negative effects of vitamin D deficiency on cardiac function, more attention should be paid to healthy individuals with vitamin D deficiency.

Multiple Molecular-Level Processes in the Evolution of Residual Strain in 3D Printed Poly(ether ether ketone)

Multiple Molecular-Level Processes in the Evolution of Residual Strain in 3D Printed Poly(ether ether ketone)

Full-Field Strain Measurements of the Muscle-Tendon Junction Using X-ray Computed Tomography and Digital Volume Correlation.

We report, for the first time, the full-field 3D strain distribution of the muscle-tendon junction (MTJ). Understanding the strain distribution at the junction is crucial for the treatment of injuries and to predict tear formation at this location. Three-dimensional full-field strain distribution of mouse MTJ was measured using X-ray computer tomography (XCT) combined with digital volume correlation (DVC) with the aim of understanding the mechanical behavior of the junction under tensile loading. The interface between the Achilles tendon and the gastrocnemius muscle was harvested from adult mice and stained using 1% phosphotungstic acid in 70% ethanol. In situ XCT combined with DVC was used to image and compute strain distribution at the MTJ under a tensile load (2.4 N). High strain measuring 120,000 µε, 160,000 µε, and 120,000 µε for the first principal stain (εp1), shear strain (γ), and von Mises strain (εVM), respectively, was measured at the MTJ and these values reduced into the body of the muscle or into the tendon. Strain is concentrated at the MTJ, which is at risk of being damaged in activities associated with excessive physical activity.

Exploring cardiovascular implications of juvenile dermatomyositis: Insights from aortic stiffness analysis and 3D echocardiography.

Our goal was to use three dimensional (3D) strain analysis to evaluate myocardial function and ascending aorta elasticity changes in juvenile dermatomyositis (JDM). Between 2019 and 2021, 23 JDM patients and 20 healthy volunteers participated. Both groups underwent 2D and 3D strain analysis, assessing aortic stiffness using aortic distensibility, stiffness index, strain, and elastic modulus. JDM patients had a median age of 13.3±5.2 years, while controls had a median age of 13.8±4.76 years. 3D strain analysis revealed significantly lower global longitudinal (GLS) and circumferential strain (GCS) in JDM patients compared to controls. Specifically, 3D GLS was notably reduced in patients (-28.1% vs. -31%, p=.047) compared to controls, and 3D GCS was also lower in patients (-27.5% vs. -30.5%, p=.019) compared to controls. Aortic strain and elastic modulus were significantly lower in JDM patients, while aortic stiffness index and distensibility showed no significant differences. Correlation analyses within the JDM group revealed a negative correlation between 3D GLS and age at diagnosis (r=-.561, p=.04), as well as a positive correlation between 3D GLS and both aortic strain (r=.514, p=.0001) and elastic modulus (r=.320, p=.03) in JDM patients. Our study demonstrated a trend towards lower ejection fraction and strain in patients with JDM, along with increased aortic stiffness using 3D echocardiography. These findings suggest potential cardiovascular involvement in juvenile dermatomyositis, emphasizing the importance of comprehensive cardiac assessments in these patients.

The Two-Domain Model Utilizing the Effective Pinning Energy for Modeling the Strain-Dependent Magnetic Permeability in Anisotropic Grain-Oriented Electrical Steels.

This paper presents a newly proposed domain wall energy-based model of the 2D strain dependence of relative magnetic permeability in highly grain-oriented anisotropic electrical steels. The model was verified utilizing grain-oriented M120-27s electrical steel sheet samples with magnetic characteristics measured by an automated experimental setup with a magnetic yoke. The model's parameters, identified in the differential evolution-based optimization process, enable a better understanding of the interaction between stress-induced anisotropy and magnetocrystalline anisotropy in electrical steels. Moreover, the consequences of the simplified description of grain-oriented magnetocrystalline anisotropy are clearly visible, which opens up the possibility for further research to improve this description.

Unlocking the Secrets of Valvular Heart Disease: A Journey through the World of Imaging Modalities

Valvular heart disease is a prevalent and clinically significant condition with potential complications and adverse outcomes if left untreated or poorly managed. Accurate assessment of valve structure, function and hemodynamics is crucial for effective evaluation and management of valvular heart disease. In this systematic review, we provide a comprehensive overview and comparison of imaging modalities used in the assessment of valvular heart disease. The introduction highlights the background and significance of valvular heart disease, emphasizing its impact on cardiovascular health, global prevalence, and associated complications. Furthermore, it emphasizes the importance of imaging modalities in the evaluation and management of valvular heart disease, discussing their role in providing crucial information for accurate diagnosis, risk stratification, treatment planning, and monitoring. The objective of this review article is to summarize the strengths, limitations and diagnostic accuracy of different imaging modalities in valvular heart disease assessment. We present detailed discussions on echocardiography, computed tomography (CT) imaging, nuclear imaging techniques and emerging imaging modalities, such as 3D echocardiography, strain imaging and fusion imaging. Each section explores the specific role of the imaging modality, its advantages, limitations and diagnostic accuracy in the evaluation of valvular heart disease. Additionally, we provide a comparative analysis of these imaging modalities, highlighting their strengths, weaknesses and specific indications. The integration of multiple imaging modalities for a comprehensive evaluation in specific scenarios is also discussed, emphasizing the complementary roles of different modalities in optimizing diagnostic accuracy and treatment planning. The review concludes with implications for clinical practice and future research directions. It underscores the importance of selecting the appropriate imaging modality or combination of modalities based on individual patient characteristics and clinical needs. Furthermore, it highlights the potential clinical impact of emerging imaging techniques and the need for standardization, cost-effectiveness studies, and further research to optimize the utilization of imaging modalities in valvular heart disease management. Bangladesh Heart Journal 2023; 39(1): 49–56

Experimental determination of strain in thin aluminum plate with central hole subjected to far-field tensile loading using digital image correlation (DIC)

A flat Aluminum specimen with a geometric discontinuity, which allows testing of the applicability of 2D and 3D Digital Image Correlation Strain measurements, has been considered for this research since it is prone to high stress concentration via Addis Ababa Institute of Technology research interest. Experimental strain using digital image correlation and geometry measurements should be measured with estimated material properties and compare the results with theoretical model predictions. Aluminum plate with central hole were subjected for far field stress in the Machine shop of School of Mechanical and Industrial Engineering at Addis Ababa University in order to test the agreement between DIC’s strain analysis, strain gauge strain analysis and calculated empirical formulas of strain analysis and for the stress distribution of the plate elastically deformed by using VIC-3D and strain gauge. The aim is to measure vertical strain field, Vertical strain along horizontal line through hole center as function of applied loading and vertical strain using theoretical formula along same line as measurements in a plate with central hole subjected to far field and near field tensile loading using visual image coloration (VIC-3D) software, Destensometere device and solid mechanics equations to compare strain results.

Assessment of left ventricular function in asthmatic children using speckle tracking and tissue doppler echocardiography

Background Acute bronchial asthma affects many organs including the cardiovascular system. Recurrent hypoxia and the production of inflammatory mediators lead to chronic inflammation, pulmonary vasoconstriction, and pulmonary hypertension, which can affect cardiac function. Aim This study aimed to assess left ventricular function in children with acute bronchial asthma using two-dimensional (2D), three-dimensional (3D) speckle tracking echocardiography (STE), and tissue doppler imaging (TDI). Patients and methods Fourty-five children with moderate persistent asthma aged 5–16 years and 15 matched controls were enrolled in this study. In addition to pulmonary function testing with spirometry, all participants underwent cardiac evaluation using conventional echocardiography, TDI, and 2D and 3D STE. Results The asthmatic children had significantly lower left ventricular systolic and diastolic functions (P = 0.017, P &lt; 0.001, respectively) but significantly higher myocardial performance index (MPI) (P &lt; 0.001) than that of the control group by TDI. By using 3D STE, 3D longitudinal strain, 3D circumferential strain, 3D area strain, and 3D radial strain were significantly lower in asthmatic children than the healthy control. Conclusion Children with asthma are more likely to have left ventricular dysfunction of different severities, which can be identified early using TDI and 3D STE.

Association between Arterial Stiffness and Higher Burden of Atrial Arrhythmia in Elderly Hypertensive Patients without Atrial Fibrillation.

Arterial stiffness is associated with higher burden of atrial arrhythmias and worsening left atrial function (conduit and reservoir), even before dilation of this cavity. PACs: premature atrial contractions; cfPWV: carotid-femoral pulse wave velocity. Increased arterial stiffness is currently an independent risk factor for atrial fibrillation, but the pathophysiological mechanisms of this arrhythmia remain an area of knowledge gap to be explored. To investigate the existence of an association between arterial stiffness and the density of premature atrial contractions (PACs) in hypertensive individuals without atrial fibrillation. Cross-sectional study with hypertensive patients without diagnosed atrial fibrillation, who were studied with speckle-tracking echocardiography to assess left atrial (LA) strain and carotid-femoral pulse wave velocity (cfPWV) to assess arterial stiffness. All patients underwent 24h-ECG Holter and laboratory tests. Significance level was set at p<0.05. Seventy participants from a single centre without overt cardiovascular disease were included. The cfPWV was correlated with higher density of PACs in 24h-Holter monitoring, independently of LV mass index (1.48 [1.08-2.03], p-value 0.005). Increased cfPWV was correlated with decreased LA strain values, with Spearman correlation coefficients of -0.27 (p-value 0.027) and -0.29 (p-value 0.018) for reservoir and conduit 2D Strain, respectively. In this study with hypertensive patients, it was possible to demonstrate an association between arterial stiffness and higher density of atrial arrhythmias. Furthermore, arterial stiffness was associated with lower left atrial strain values for reservoir and conduit functions.

Assessment of low-velocity impact response of a hybrid carbon-aramid braided composite by algorithmic quantification of volumetric structures

This work investigates the impact response of a hybrid two-dimensional (2D) tubular braided composite through an ex-situ examination of its internal structure. An inter-ply hybrid laminate of biaxial braided carbon and aramid layers was manufactured. The sample underwent split Hopkinson pressure bar (SHPB) impact testing, where the applied energy induced barely visible impact damage (BVID). Volumetric representations of the sample were created before and after impact testing using micro-computed tomography (µCT). Novel algorithms were developed to assess properties of the braided composite sample. First, voids in the sample before and after impact were identified through a series of image processing techniques, after which various void properties were extracted. Each void was then matched between datasets to track property change caused by impact. Next, damage in the sample after impact was identified through another series of image processing techniques, then quantified and characterized in the context of the full sample. Statistical analyses in the form of paired-sample t-tests were performed for void properties and overall surface topologies. Additionally, measurement of 3D strain within selected regions of the sample was performed using digital volume correlation (DVC). Results showed that the impact damage did not cause significant void enlargement, but instead caused surface topology shifts, particularly at the inner surface, owing to plastic deformations caused by impact damage, which were primarily caused by delamination and developed from large voids at the site of impact. The hybrid material configuration exhibited a phenomenon where the inner and outer layers minimized cracking in the middle layer, causing plastic deformation to be the primary impact response of the middle layer. Through the analysis processes developed in this work, quantitative assessment of tubular braided composites was achieved by measuring changes in voids caused by impact at the individual level, and by examining the damage profile while accounting for the voids. The methodology can be applied to various material configurations to provide meaningful insight into the effects of hybridization in the impact response of braided composites.