Shear Stress Research Articles

Comparison of airway resistance and wall shear stress between non- and bronchial pattern images in cats by computational simulation

Comparison of airway resistance and wall shear stress between non- and bronchial pattern images in cats by computational simulation

Improvement on gel properties of chicken myofibrillar protein with electron beam irradiation: Based on protein structure, gel quality, water state

This study aimed to investigate the effects of electron beam (E-beam) irradiation at different doses (0–15 kGy) on the solubility, rheological properties, emulsification characteristics, and moisture distribution of chicken myofibrillar proteins (MPs). Irradiation treatment notably increased the solubility, surface hydrophobicity, emulsification properties, and apparent viscosity of MPs, based on conformational changes caused by irradiation-induced oxidative denaturation of proteins. However, high doses of irradiation (15 kGy) induced in excessive cross-linking and aggregation of proteins, reducing the solubility, emulsification properties, and shear stress. Degradation of myosin heavy and light chains in irradiated MPs increased the content of β-turns and random coils. Additionally, the initial relaxation times of T21 and T22 in irradiated protein gels were reduced, and the peak value of P21 was increased, which improved the water-capturing ability of protein gels. Altogether, these results findings suggest that electron beam irradiation can be applied as a potential technique for modifying muscle proteins.

The Shear Performance of DSCW-RC Joints with Lap-spliced Steel Bars

The double steel plate concrete composite shear wall (DSCW) structure combines the advantages of steel and concrete, offering high strength, stiffness, and durability. The joint formed by the DSCW and reinforced concrete foundation (RC foundation) was often unavoidable in engineering practice. Research related to the mechanical behavior of the DSCW-RC foundation is limited. This paper investigated the shear performance of DSCW-RC joints with lap-spliced steel bars. A total of seven specimens were designed and tested. The influences of steel plate thickness, steel bar arrangement, and stud spacing on the shear behavior of the joints are elucidated. The test results indicate that the predominant failure mode of the specimens occurred in the upper part of the local steel plate, with reinforcement yielding. While steel bar diameter and stud spacing minimally affected the shear strength, they significantly influenced the failure displacement at the joint interface. The failure deformation increased with increasing steel bar diameter and decreased with increasing stud spacing. Moreover, the thickness of the steel plate profoundly impacted structural shear strength and deformation, with both deformation and bearing capacity increasing with plate thickness. In addition, this study explores the force-transferring mechanism of such joints under shear load, offering a crucial reference for subsequent analyses of the composite force mechanism of DSCW - RC foundation joints.

Computational analysis on 3D airway model of obstructive sleep apnea patient for optimal maxillomandibular advancement.

Obstructive sleep apnea (OSA) can have many adverse effects on people's health, including cognitive decline and high blood pressure. Typical surgical treatment methods include the commonly performed uvulopalatopharyngoplasty and the highly successful maxillomandibular advancement (MMA). These surgical methods are more effective than non-surgical methods because they widen the airway where a collapse has occurred through direct treatment. However, few studies has shown that moving the upper and lower jaws in a specific manner is the most efficient way to treat OSA during an MMA surgery. In this study, the airway of an OSA patient was reproduced digitally, and computational fluid dynamics analysis was performed on various models with changed airway shapes, including the original model based on an actual CT image and three resizing models of the retropalatal (RP) and retroglossal (RG) regions of the airway. Consequently, it was possible to provide more quantitative predicted flow data, which could be helpful in performing sophisticated OSA surgery. Among the four airway models of the OSA patient, a reduction in the epiglottis regional pressure difference of up to 40.2% was evident in the model with an expanded RG region, and a reduction in the wall shear stress of up to 25.8% was confirmed. The proposed process could be an important aid for surgeons in determining the optimal surgical method suitable for an individual patient's uniquely-shaped airway.

Investigating the Mechanism of Banxia Xiexin Decoction in Treating Gastritis and Diabetes Mellitus through Network Pharmacology and Molecular Docking Analysis

Background: Banxia Xiexin decoration (BXD), a complex prescription in Traditional Chinese Medicine (TCM), clinically acts as a treatment for gastritis and diabetes while its mechanism of treatment remains unknown. Objection: This study aimed to explore the common mechanism of BXD in treating gastritis and diabetes based on network pharmacology and molecular docking technology. Methods: The seven Chinese herbal components and drug targets were collected from the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP) for gastritis and diabetes using GeneCards, DisGeNET, Comparative Toxicogenomics Database (CTD), and Online Mendelian Inheritance in Man (OMIM) databases. Common drug and disease targets were imported into the STRING data platform for protein-protein interaction (PPI) analysis, and Cytoscape 3.7.2 software for network topology analysis, and core targets were filtered. Results: There were 124 components, 249 targets, 449 targets for gastritis, and 4005 targets for diabetes. After mapping, 83 BXD targets for gastritis and diabetes were obtained, and the targets with high correlation were STAT 3, JUN, TNF, IL-6, etc. More relevant targets were involved in the cancer pathway, AGE-RAGE signaling pathway of diabetic complications, fluid shear stress, and atherosclerosis pathway. Conclusion: This study preliminarily reveals that BXD may play a role in the treatment of gastritis and diabetes mellitus through multi-components, multi-targets, and multi-pathways, and proposes some potential "component-target-pathway" hypotheses in light of previous reports.

Mechanical Characteristics of Similar Weakly Cemented Soft Rock under Directional Shear Stress Path and Modified Lade–Duncan Criterion

Mechanical Characteristics of Similar Weakly Cemented Soft Rock under Directional Shear Stress Path and Modified Lade–Duncan Criterion

A Hydraulic Gradient and Stress-Controlled Erosion Apparatus for Assessing Soil Internal Erosion

Abstract Among the four dominant mechanisms of internal erosion, suffusion appears as one of the most complex. It is indeed the result of the combination of three processes: dislodgement of fine particles, transport of them, and filtration of some fluidized fine particles. These processes depend on the soil’s stress state and on the hydraulic gradient path. Thus, to ensure the repeatability of the suffusion test and to study with accuracy the influence of the aforementioned parameters, a new apparatus was developed. This apparatus is designed to test specimens under a vertical downward flow in hydraulic gradient controlled condition while controlling the confining pressure and the stress deviator, which can be either positive or negative. Ten tests on one cohesionless soil were performed in triaxial conditions, with the same mean effective stress and four different values of stress deviator. To compare with conventional suffusion results, one test is also performed in rigid wall conditions. For all performed tests, the same hydraulic gradient path was applied and particular attention is paid to the repeatability, which implies control of each test step. At the end of each test, the specimen was divided into four layers to measure post-suffusion grain size distributions. The time evolutions of the hydraulic conductivity and the erosion rate permit to identify four different phases. Each phase is characterized by two methods: one based on the hydraulic gradient and the second based on the expended energy by the fluid. The results show the great influence on the suffusion kinetics of the preferential flow paths, which localize in the body of the specimen in triaxial conditions and on the circumference in rigid wall ones. Under a constant mean effective stress, the effect of the stress deviator on the suffusion kinetics appears limited, for the tested soil and shear stress ratios.

Preventing scour of monopile foundations using a vertical rotation device

Scour around monopile foundations is a major cause of offshore wind turbine failures, necessitating effective scour prevention measures to ensure the reliability of monopiles. This study investigates a new scour prevention strategy utilizing a vertical turbine rotor. This measure can not only effectively reduce scour around monopile foundations in complex flow field environments but also generate clean electricity, adding value. The effectiveness of the device in mitigating scour is evaluated through experiments. Subsequently, the impact of the flow field around the pile foundation and the seabed shear stress are examined using numerical simulations. The influence of the device’s installation position on seabed shear stress is also discussed. The results indicate that the vertical rotating device significantly reduce scour around the pile foundation, thereby enhancing the reliability of monopile foundations.

Effect of Blade Thickness on Hemodynamics and Hemolysis: A Case Study of Pediatric Centrifugal Blood Pumps.

Blood pumps have become popular whether for use as an implantable ventricular assist device or as extracorporeal membrane oxygenation. The quality of these pumps is assessed according to their ability to reduce the risk of blood damage thanks to an optimal choice of their geometric and operating properties. Lack of the research focused on the geometrical optimization of impellers has prompted this study. This study evaluated a computational and experimental analysis comparing the hemolytic performance of three centrifugal pumps. For this purpose, methods of Eulerian and Lagrangian are respectively used for hemodynamic and hemocompatibility investigations. Referring to the pediatric demands, these pumps function under clinically applicable pressure-flow conditions: 1 l/min of blood flow and a pressure differential of 60 mm Hg. These three pumps all use the same volute, but their impellers differ in terms of blade thickness. The objective is to examine how surface area affects the generation of hemolysis. In silico simulations were employed for both of the following tasks: first, identifying the distributions of velocities, pressures, and shear stresses; second, applying the Lagrangian approach to estimate the hemolysis index. Results showed the importance of the flow passage and the surface of the clearance on the hemocompatibility of the pumps. However, it was observed that there is not a linear effect of the blade thickness on the shear stress or index of hemolysis. Additionally, this work can provide information to develop an optimal design of a more hemocompatible blood pump.

Prognostic significance of pre-procedure wall shear stress in the ascending aorta in patients with aortic stenosis undergoing transcatheter aortic valve replacement

Abstract Background Accurate prognostication before the procedure is challenging in patients with aortic stenosis (AS) undergoing transcatheter aortic valve replacement (TAVR). Recently, blood flow dynamics assessed by four-dimensional flow cardiovascular magnetic resonance imaging (4D-flow CMR) showed a significant reduction in average wall shear stress (WSS) in the ascending aorta (AAo) after TAVR. However, the prognostic value of pre-procedure average WSS in the AAo is controversial. Purpose We aimed to investigate whether pre-procedure average WSS was associated with clinical outcomes in patients with AS undergoing TAVR. Methods We prospectively examined 159 consecutive AS patients who underwent TAVR (57 males, mean age 83.6 ± 4.7 years, median left ventricular ejection fraction 63.4%) between May 2018 and May 2022. We assessed average WSS in the AAo before TAVR using 4D-flow CMR. We divided the patients into high WSS (≥6.60 Pa, n = 79) and low WSS (<6.60 Pa, n = 80) groups according to the median value of pre-TAVR WSS. The primary outcome of interest was a composite of all-cause death and hospitalization for worsening heart failure. Results Patients with high WSS had lower age compared to those with low WSS. There were no significant differences on sex, body mass index, systolic blood pressure, hemoglobin, serum albumin, N-terminal pro b-type natriuretic peptide, left ventricular ejection fraction, mean transaortic valvular gradient, annulus area in aortic valve and AAo diameter between the groups. During a median follow-up period of 19.8 months (interquartile range 6.0-37.1), the primary outcome more frequently occurred in patients with low WSS than in those with high WSS (28% vs 5%, P <0.001) (Figure 1). A multivariable Cox regression showed that lower WSS independently associated with increased risk of the primary outcome (hazard ratio 0.69, 95% confidence interval [CI] 0.53-0.91, P <0.001), even after adjustment for significant prognostic covariates including age, sex, serum albumin, history of chronic obstructive pulmonary disease, peripheral artery disease and malignancy, and estimated glomerular filtration rate. Predictive performance for the primary outcome was improved when adding the value of WSS in the AAo to representative prognostic factors (c-index 0.81 95%CI 0.72-0.90 vs. 0.77 95%CI 0.67-0.88) (Figure 2). Conclusions In patients with AS who underwent TAVR, lower average WSS in the AAo before procedure was associated with higher risk of worse clinical outcomes, suggesting that pre-TAVR average WSS in the AAo would be a surrogate marker and useful for the risk stratification.Survival analysis for primary outcomePredictive performance

Prognostic value of circulating glypican-4 in patients with chronic heart failure with reduced ejection fraction

Abstract Background Chronic heart failure is one of the leading causes of hospitalization and mortality worldwide, with an ever-increasing prevalence. Glypican-4 (GPC4) is a cell surface protein part of the endothelial glycocalyx which is actively released into the circulation in the context of ischemia, inflammation, neurohumoral activity, and shear stress. The current literature on the association between circulating GPC4 and heart failure is limited and its prognostic value on top of established risk markers in chronic heart failure is unknown. Purpose In the present study, we aim to investigate the prognostic value of circulating GPC4 on clinical outcomes in a contemporary cohort of patients with stable chronic heart failure with reduced ejection fraction (HFrEF). Methods Symptomatic outpatients with stable chronic HFrEF were consecutively enrolled in a prospective cohort study. Circulating serum GPC4 levels were assessed using an enzyme-linked immunosorbent at baseline. Patient outcomes were retrieved from medical and health insurance records. Results We enrolled 205 patients with a median (interquartile range) age of 66 (59-74) years, with 22% females. Median left ventricular ejection fraction (LVEF) was 37 (30-43)%, median estimated glomerular filtration rate (eGFR) was 64 (48-80) ml/min/1,73 m2, median N-terminal pro-brain natriuretic peptide (NT-proBNP) was 964 (336-2173) pg/ml, median interleukin 6 (IL6) was 4.7 (3.2-7.9) pg/ml, and median GPC4 was 1553 (1034-1950) pg/ml. During a median follow-up of 4.7 (4.0-5.3) years, 46 patients (22%) were hospitalized due to worsening heart failure (WHF), 18 patients (9%) died of cardiovascular (CV) cause, and 58 patients (28%) died of any cause. In univariate Cox-regression, serum GPC4 levels predicted WHF (HR 1.57, 95%CI 1.29-1.92, p<0.001), CV death (HR 2.07, 95%CI 1.56-2.74, p<0.001), and all-cause mortality (HR 1.93, 95%CI 1.59-2.34, p<0.001). The association between serum GPC4 levels and both, CV death (HR 1.69, 95%CI 1.04-2.86, p=0.048) and all-cause mortality (HR 1.56, 95%CI 1.14-2.14, p=0.006) remained significant in a multivariable Cox-regression model adjusted for age, sex, eGFR, IL6, NT-proBNP, and LVEF. Conclusion In patients with stable chronic HFrEF, circulating GPC4 is significantly associated with cardiovascular outcome and is an independent predictor of all-cause mortality. The potential prognostic value in clinical routine of GPC4 should be addressed in prospective studies.

Effects of calcium pidolate on performance, carcass traits, bone biomechanical properties and mineralisation and jejunum histomorphology in broilers

ABSTRACT 1. The current study was conducted to determine the effect of dietary calcium pidolate (CalP) on performance, slaughtering characteristics, bone biomechanical properties, mineralisation and jejunum histomorphology in male broilers. A total of 200 one-day-old Ross 308 male chicks were randomly assigned to one of four treatments as five pen replicates, each containing 10 chicks. The basal diet without CalP was formulated to supply the nutritional needs of broilers and the treatment diets contained 0.30, 0.45 and 0.60 g/kg CalP, with limestone meeting the remaining calcium requirement. 2. The addition of CalP had a quadratic effect on performance (P < 0.05) and the best performance was achieved in the group that included CalP at a dose of 0.45 g/kg but 0.60 g/kg level worsened performance. Supplementing with CalP linearly decreased carcass yield (P < 0.01) and relative breast weight (P ≤ 0.05) but the relative thigh weight increased quadratically (P < 0.05) and reached a maximum at 0.45 g/kg. 3. Tibia shear force and stress linearly increased with the use of CalP in the diet (P < 0.05). Supplementation had a quadratic effect on tibial calcium (P < 0.01), reaching a maximum at 0.30 g/kg, although tibial phosphorus levels decreased linearly (P < 0.01). 4. The effect of CalP on jejunum histomorphology fluctuated and, compared to the unsupplemented control group, the villus height/crypt depth ratio increased, while the other variables decreased (P < 0.05). Decrease in crypt depth with the addition of CalP was significant (P < 0.05). 5. Using Ca-pidolate at a rate of 0.45 g/kg in broiler diets is sufficient to increase performance and tibia strength but 0.60 g/kg level negatively affected performance. In addition, the results of jejunum histomorphology were variable, but the crypt depth decreased with CalP levels and this is an important effect. However, further research is needed to detail the effect of CalP on broilers.

The implantation of a left ventricular assist device causes changes in the aortic miRNome and proteome - an integrative analysis

Abstract Background Left ventricular assist devices (LVAD) have been widely used and accepted to treat patients with end-stage heart failure. LVAD non-physiological blood flow velocity, wall shear stress distribution, vorticity current intensity, and vorticity flow generation affect the pathophysiology of vascular changes in aortic tissue. Purpose In this study, we performed multi-omics-based analysis of the aorta to identify molecular markers that could clarify vascular remodeling during LVAD support. Methods Aortic specimens from 48 patients (pair matched samples N=96) were excised during implantation and explantation of LVAD. Small RNA-Seq screening using Next Generation Sequencing and proteomic profile using Data-Independent Acquisition mass spectroscopy were conducted. Experimental and computational approaches, proteomics and transcriptomics data, were integrated and bioinformatics analyses were performed. Results The principal component analysis of miRNome and permutational multivariate analysis of variance of proteomic profile clearly segregated samples before and after LVAD support. We identified a total of 113 differently expressed (DE) miRNAs (61 up-regulated; Padj&amp;lt;0.05 and log2 fold change&amp;gt;|0.5|) after long-term LVAD support. Proteomic analysis identified in total 93 protein significantly changed (47 increased; Padj&amp;lt;0.05 and log2 fold change&amp;gt;|0.5|). Correlation analysis identified strong association between 270 proteins and 66 DE-miRNAs (Padj&amp;lt;0.05 and correlation coefficient&amp;gt;|0.7|). Gene Set Enrichment Analysis revealed, that predicted target genes of DE-miRNAs were mainly engaged in axon guidance, regulation of actin cytoskeleton, endocytosis, and MAP signaling pathway (Padj&amp;lt;0.05). DE-proteins participated mainly in ECM-receptor interaction, focal adhesion, and platelet activation (Padj&amp;lt;0.05). Conclusion Our study presents a network-based method of integrating microRNAs and proteome data and reveals molecular signatures that reflects aortic vascular remodeling due to LVAD treatment.PCA of miRNA DESeq2PCA of protemic profile

Investigation of Scaling and Materials’ Performance in Simulated Geothermal Brine

Geothermal energy generation faces challenges in efficiency, partly due to restrictions on reinjection temperatures caused by scaling issues. Therefore, developing strategies to prevent scaling is critical. This study aims to simulate the scaling tendencies and corrosion effects of geothermal fluids on various construction materials used in scaling reactor/retention tank systems. A range of materials, including carbon steel, austenitic stainless steel, duplex stainless steel, two proprietary two-part epoxy coatings, and thermally sprayed aluminium (TSA), were tested in a simulated geothermal brine. Experiments were conducted in a laboratory vessel designed to replicate the wall shear stress conditions expected in a scaling reactor. The tests revealed varying scaling tendencies among the materials, with minimal corrosion observed. The dominant scale formed was calcium carbonate, consistent with geochemical modelling. The findings suggest that despite the high operating temperatures, the risk of corrosion remains low due to the brine’s low chloride content, while the wettability of materials after immersion may serve as a useful indicator for selecting those that promote scaling.

Regional distribution of diffuse fibrosis in the basal and mid-ventricular AHA segments in patients with type 2 diabetes

Abstract Introduction Cardiovascular magnetic resonance (CMR) research including from our research group, has documented that patients (pts.) with type 2 diabetes (DM2) even without symptoms exhibit subtle to moderately increased myocardial extracellular volume (ECV). ECV is an imaging biomarker of diffuse fibrosis. Also, our prior research has revealed a prevalence of approx. 10% for non-ischemic late gadolinium enhancement (LGE). Intriguingly, these LGE lesions manifested in a distinct pattern, situated in the basal lateral or infero-lateral positions. We postulate that these lesions may represent the end-stage of severe diffuse fibrosis, potentially influenced by factors such as increased shear wall stress. Purpose To investigate if pts. with DM2 with known high global ECV had higher regional ECV in the basal and lateral or infero-lateral AHA segments compared to other segments. Method A case-control study of 20 healthy controls, 20 pts. with DM2 with low ECV (ECV&amp;lt;28%), 20 pts. with DM2 with high ECV (ECV&amp;gt;29%), and 20 pts. with DM2 with non-ischemic LGE (LGE+). Pts. were identified from a cross-sectional cohort of pts. with DM2. All subjects underwent physical examination and extensive CMR with T1 mapping before and after gadolinium contrast, and myocardial perfusion at rest and during adenosine stress. The regional ECV values for the basal and the mid-ventricular short axis slide were analysed using the AHA segments model: segments 1 to 12. Results All groups (grp.) had comparable age and sex distribution. In the DM2 grp. there was a difference between the no. of pts. with DM2 duration &amp;gt;10 years (low ECV 11(55%), high ECV 12(60%), LGE+ 16(80%), however statistically significant. Global ECV were: Controls (mean±sd) 26.7±1.6%, Low ECV 26.3±1.4%, High ECV 32.0±2.9%, LGE+ 29.5±2.6%, p&amp;lt;0.001. Control subjects had regional ECV between 24.4±2% to 27.3±2% (p&amp;lt;0.001), highest values in the septum. The DM2 grp. with low ECV had regional ECV values of 24.5±3% to 29.2±4%, highest values in the basal inferior and septal parts (segments 2-4). The high ECV grp. had regional ECV values between 28.3±4% and 35.3±6 % with very high values in the basal and the mid-ventricular septum, inferior, and inferolateral part (segments 2-5 and 8-11). The DM2 group LGE+ had values between 26.6±3% and 34.5±7%, highest values in the basal slice in the septum, inferior, and infero-lateral parts (segments 2-5). We found no significant difference in the regional myocardial perfusion reserve index. Conclusion This evidence indicates that diffuse fibrosis in DM2 cardiomyopathy tends to concentrate in the septum and inferolateral regions. However, among pts. with non-ischemic LGE lesions, we observed normal ECV in the anterior segments, in contrast to the high ECV group where all segments exceeded normal levels, albeit with notable regional variations. Subsequent investigations should prioritize uncovering the underlying reasons for this specific regional distribution of diffuse fibrosis.AHA segments 1-12 mapsAHA segments 1-12 maps

Microdosing of alteplase leads to thrombolysis in an in vitro flow model of cardiac microvascular obstruction

Abstract Background Cardiac microvascular obstruction (MVO) is a frequent injury of the myocardial microcirculation after successful recanalisation of the occluded coronary artery in myocardial infarction. At least in part, MVO is caused by embolised microthrombi of less than 200 µm diameter [1]. MVO leads to hypoperfusion of the myocardium and negatively affects patient outcomes. However, there is no effective treatment for MVO [2, 3]. Thrombolytic drugs are a promising approach, but they are difficult to deliver to the MVO area, and an increased risk of bleeding limits their use. In a previous study using an in vitro fluidic multi-scale model for MVO [4, 5], it was shown that controlled flow infusion (CFI) with a novel drug-delivering catheter could be used to effectively deliver highly concentrated intracoronary microdoses of a thrombolytic drug to the MVO area [6]. We now aim to investigate how such locally administered drug microdoses can induce thrombolysis as a possible therapeutic approach for MVO treatment. Methods A microfluidic chip (Fig.1) was used to study thrombolysis under flow using different microdoses of the thrombolytic drug alteplase. The chip consists of a tapered straight channel, which traps injected porcine microthrombi without causing complete channel occlusion (Fig. 1A). To mimic intracoronary CFI (consisting of temporary balloon occlusion of a coronary vessel for 90 seconds while drug is injected distally through a catheter) in vitro, microthrombi were incubated (without flow) directly in the chip for 90 seconds with various microdoses of alteplase (Fig. 2A, C). The chip was subsequently perfused with porcine plasma for 25 min (matched for physiological shear stress of 30 dyn/cm²). Conventional intravenous (IV) drug infusion (10 mg dose) resulting in a low systemic alteplase concentration, was mimicked by perfusing microthrombi with porcine plasma containing 2 µg/ml alteplase (Fig. 2B, C). Results Thrombolysis after CFI was concentration dependent, with the lowest microdose (0.3 mg) achieving 24% lysis of the thrombus area and the highest microdose (1.5 mg) achieving 60% lysis. In contrast, conventional IV drug infusion (corresponding to 10 mg alteplase IV dose) only achieved 10% lysis and was not significantly higher than the control perfused with pure porcine plasma. Conclusion Our findings suggest that intracoronary CFI is more efficient at achieving porcine microthrombus lysis than the current standard of IV bolus infusion (2 µg/ml alteplase in the circulating blood). Intracoronary CFI microdosing of fibrinolytic drugs using a drug-delivering catheter is a promising therapeutic approach for treating embolising MVO with a reduced systemic drug burden. Importantly, our intracoronary CFI approach achieves locally 6–40 times higher drug concentrations than a conventional IV drug infusion while reducing the total drug dose 60–300 times (Fig. 2C).

Enhancing computational fluid dynamics simulation for coronary artery disease analysis through spatial iterative modeling

Abstract Background Endothelial shear stress (ESS) critically influences the pathogenesis of coronary artery disease (CAD) by modulating the formation and progression of atherosclerotic lesions. Despite the use of 3D modeling in computational fluid dynamics (CFD) simulations to calculate ESS, the precision of these models significantly depends on the method of reconstruction. Spatial Iterative Method (SIM) extends the iterative approach in computer science to spatial data, using recurring algorithms to refine 3D models and analyses. Iterative approach executes a sequence of instructions repeatedly until a certain condition is met, enabling progressive problem-solving. Purpose In this study, we investigated the application of the SIM to estimate ESS in coronary arteries and explored Atherosclerotic Plaque Areas (APA) in patients with CAD. Methods We analyzed fifteen patients (9 males, mean age of 63 ± 10.56 years) with atherosclerotic plaque on coronary arteries. The eighteen images captured from an anterior viewpoint in 10-degree increments of the coronary artery obtained from Coronary Computed Tomography Angiography at the best diastolic phase for each patient were used. We implemented the SIM for 3D model reconstruction, facilitating ninety comparisons across all iterations to evaluate ESS estimations accurately. (Figure 1.) Results In our study, we evaluated ESS contours from CFD simulations for a total of 282 APA (200 calcified and 82 soft plaques) across ninety spatial iterations. We categorized ESS into three groups: low (162 APA cases with ESS of less than 1 Pascal (Pa)), medium (67 APA cases with ESS between 1 and 2 Pa), and high (53 APA cases with ESS greater than 2 Pa). There was a significant association between ESS categories and plaque types (p &amp;lt; 0.0001, Figure 2.). The calcified plaques were formed in areas with low ESS (%80 of calcified plaques) and soft plaques in areas with medium and high ESS (%97 percent of soft plaques). Conclusion The significant association between ESS categories and plaque types shows the potential of SIM in hemodynamic analysis. This finding highlights the potential of SIM in enhancing the understanding of hemodynamic influences on plaque formation, offering a promising direction for future cardiovascular research.Figure 1.Sample Iteration of the SIMFigure 2.Heatmap of ESS vs. APA

Identification of left ventricular flow features in healthy and pathological conditions

Abstract Background In the presence of mitral valve diseases or following surgical interventions, the hemodynamics in the left ventricle (LV) are significantly altered [1]. These maladaptive intraventricular hemodynamic alterations can stimulate a cascade of events leading to progressive adverse LV remodeling and eventual heart failure [2]. Qualitative and quantitative evaluation of LV flow features may provide a potential for sensitive risk stratification of clinical cardiac function [3]. Purpose The purpose of this study is to identifying LV flow features using in vitro experiments under both normal and pathological conditions, including mitral regurgitation (MR), mitral valve replacement with bioprosthetic/mechanical valve, and transcatheter mitral valve edge-to-edge repair (TEER). Methods We utilized a biohybrid approach to construct the in vitro experimental platform, where the native mitral valve (including chordae tendineae and papillary muscles) and aortic valve from porcine were combined with a 3D-printed silicon LV (figure 1). To ensure comparability across different conditions, we maintained consistency by utilizing the same native valve and 3D-printed LV. For pathological conditions, we cut the chordae tendineae in A2 zone to induce the severe degenerative MR, and TEER was performed on this prolapsed valve by placing two clips in A2-P2 zone. Then, the anterior leaflet of valve was cut, and a bioprosthetic valve and mechanical valve were sutured to mitral annulus to simulate surgical valve replacement, respectively. Left ventricular flow fields were measured using four-dimensional particle image velocimetry (4D-PIV) technique, with vector interval of 0.9 mm in all the spatial directions and temporal resolution of 10 ms. Results Significant differences in mean flow field were observed among healthy and pathological conditions (figure 2). Firstly, the vortex orientation was clockwise in healthy, MR, bioprosthetic valve replacement, and TEER conditions, which could accompany the redirection of blood flows towards the aortic valve. However, the replacement with a mechanical valve resulted in an alteration in vortex orientation from clockwise to counterclockwise. Secondly, the position of the center of the vortex changed in pathological conditions, with the center of the vortex closest to the apex and the left ventricle outflow tract in the healthy condition. Thirdly, the maximum Reynolds shear stress (RSS), which may be responsible for thrombus formation, significantly increased after TEER procedure and bioprosthetic valve replacement. Conclusions This study demonstrates significant changes in LV hemodynamics across different conditions. The flow features, including vortex orientations, vortex positions and the RSS, may potentially become crucial considerations for the optimization of artificial valves and mitral valve repair devices.Figure 1 Figure 2

Capillary Orientation and Morphology Dictated Oscillatory Electro-magneto-imbibition of Viscoelastic Electrolytes.

We explore the intricate dynamics of imbibition by a viscoelastic electrolyte within an arbitrarily oriented, nonuniform microcapillary, while under the stimulus of external electromagnetic fields and internal electroviscous forces stemming from streaming potential. The microcapillary walls are envisaged to be tapered relative to each other, with the entire system inclined with respect to the horizontal plane. The rheological behavior of the electrolyte is characterized using the Phan-Thien-Tanner (PTT) model. To manipulate the imbibition dynamics, external transverse magnetic and electric fields are imposed. Incorporating all contributing forces, we obtain semianalytical formulations for the velocity and shear stress distributions. We identify distinct stages during the imbibition process: (i) initial, (ii) filling, (iii) oscillatory, and (iv) stagnation stages. Moreover, we scrutinize the impact of four pivotal parameters, namely, the Weissenberg number (Wi), the Hartmann number (Ha), the transverse electric to viscous force (EVF) number (S), and the electric Reynolds number (Ree), on the imbibition dynamics across different inclinations and taper angles. We also delineate the parameter space for these four parameters, identifying where the onset of oscillations occurs. Finally, through scaling analysis, we establish the existence of four distinct regimes corresponding to the aforementioned stages: (i) the linear regime, (ii) the Washburn regime, (iii) the oscillatory regime, and (iv) the equilibrium regime. Our findings are anticipated to enhance the understanding of capillary imbibition under such complex flow conditions and contribute significantly to the advancement of capillarity-driven microfluidic devices.

Influence of disturbed blood flow on endothelial function in people living with HIV

Abstract Introduction People infected with human immunodeficiency virus (HIV) are more susceptible to endothelial dysfunction due to the virus itself, side effects of the antiretroviral therapy and classical risk factors. Endothelial damage is most prominent at the locations where laminar blood flow is disturbed and oscillatory shear stress with retrograde blood flow is dominating. Purpose The goal of this study was to assess the endothelial function in people with HIV, and to determine whether their endothelium is more susceptible to a short-term increase in retrograde blood flow in comparison to healthy individuals. Methods The study included 62 people with HIV infection and 38 people without HIV infection, in whom endothelial function was assessed using flow-mediated dilatation, which was presented in absolute (FMD) and relative (FMD%) values. The intervention produced oscillatory shear stress and retrograde blood flow during 20 minutes, after which the endothelial function assessment was repeated. Results Baseline FMD (0.30±0.07 vs. 0.36±0.07 mm; p&amp;lt;0.05) and FMD% (6.84±1.57 vs. 7.89±1.19 %, p&amp;lt;0.05) were lower in the HIV group in compare to controls. FMD and FMD% decreased in the HIV group by 0.03 mm and 0.7% (p&amp;lt;0.05), while in the control group they decreased by 0.09 mm and 2.0% (p&amp;lt;0.05). The post-intervention FMD and FMD% were not different between the groups (p&amp;gt;0.05). Conclusion People with HIV infection express worse endothelial function in compare to healthy individuals. Retrograde blood flow and oscillatory shear stress deteriorate endothelial function in both HIV patients and healthy controls, although this decline is more pronounced in healthy individuals.