Connecting bulk rheology, structural transitions and heterogeneous flow in Pluronic F127 micellar cubic liquid crystals using rheo-microscopy.

Rheological tests (low-amplitude oscillatory shear, creep and creep recovery, and steady shear rate) were used to evaluate the 3D concrete printing (3DCP) performance of fiber-reinforced cementitious composites (FRCC). UHMWPE fibers were modified to increase hydrophilicity and functionality. FRCC with hydrophilic or hydrophobic fibers, with or without nanoclay, was assessed for extrudability and buildability. Hydrophilic fibers significantly enhanced microstructural rigidity, followed by hydrophobic fibers and nanoclay, evidenced through an increase of storage modulus by 115.29%, 59.37%, and 49.49%, respectively. The combined inclusion of hydrophilic fibers and nanoclay developed the stiffest, strongest, and stable solid-like microstructure with 211.52% enhanced storage modulus, 87.20% lowered creep compliance, 100% elastic recovery, and the highest viscoelastic yield stress, as compared to a simple cement/water mixture. Hydrophobic fibers with nanoclay also improved storage modulus and yield stresses, enabling effective buildability and extrudability. Certain FRCC compositions succeeded in 3DCP extrusion tests due to higher storage modulus and optimal yield stresses. The tensile strength and ductility of printed samples containing hydrophilic fibers improved due to stronger fiber-matrix bonding, as reflected by 40% higher first-crack strength, 19% higher ultimate tensile strength, and 50.27% enhanced strain capacity as compared to samples with hydrophobic fibers. The addition of nanoclay further improved the matrix strength in both cases. However, the ductility of FRCC containing hydrophilic fibers with nanoclay decreases by more than 50% compared to FRCC with only hydrophilic fibers, likely due to insufficient water availability to satisfy the demand of both water-absorbing components in the FRCC system. Overall, FRCC containing hydrophilic fibers without nanoclay is found to be the most effective option for 3DCP performance, demonstrating superior rheological behavior, tensile strength, and ductility.

This study investigates the dynamic response of emulsion flocculation network structures under shear loading, which is of great significance for the development of efficient flow assurance technologies. Through large amplitude oscillatory shear experiments and yield experiments on crude oil emulsion gel structures, the following findings were obtained: an increase in stirring rate enhances the yield stress and strength of the gel structure, but the promoting effect weakens after a certain intensity is reached. The analysis of yield behavior based on dissipated energy indicates that the contribution of stirring rate to the structural strength of emulsions with different water cuts varies across different strain stages. A stage-divided yield model was established, using the three-parameter solid model, Bingham model, etc., to describe the yield process. Each model demonstrates excellent fitting performance, accurately reflecting the mechanical characteristics of emulsions at different yield stages. This research provides guiding value for the development of high-efficiency flow safety technologies for waxy crude oil emulsions.

Intracranial carotid dissecting aneurysms (DA) are often treated emergently upon diagnosis. In contrast, extracranial DA are generally considered less likely to rupture and are commonly managed conservatively. Despite these clinical differences, limited data exists on the hemodynamic differences that might explain their divergent clinical behaviors. Retrospective analysis of intracranial and extracranial DA treated between 2011 to 2023. DA were reconstructed from computerized angiographic images using 3D Slicer software. Computational fluid dynamics (CFD) simulations were performed using ANSYS® Fluent package. Hemodynamic parameters calculated included time averaged wall shear stress (TAWSS), high shear areas (HSA), low shear areas (LSA), time averaged wall shear stress ratio (TAWSR), oscillatory shear index (OSI), and relative residence time (RRT). We compared these variables between extracranial and intracranial lesions using Mann-Whitney U and t-tests. Nineteen DA (10 extracranial, 9 intracranial) from 16 patients (age 48-82; 9 male) were analyzed. The average volume and area of the lesions evaluated were 187 mm3 and 158.6 mm2. Two of the intracranial DA were identified in the setting of subarachnoid hemorrhage. Extracranial DA showed significantly greater volume (234.6 vs. 83.0 mm3; p = 0.02) and area (210.9 vs. 59.4 mm2; p = 0.03). Intracranial DA demonstrated nonsignificant trends toward lower TAWSS at the aneurysm (1.04 vs. 1.53Pa; p = 0.62), lower TAWSSR (0.49 vs. 0.7; p = 0.19), greater LSA (4.2% vs. 2.7%; p = 0.28) and higher RRT (2.16 vs. 1.36 m2/N; p = 0.29). This study identified hemodynamic trends in intracranial DA (higher LSA and higher vessel wall TAWSS in relation to the DA) that may account for the differential clinical behavior and increased risk of rupture.

Computational fluid dynamics (CFD) is commonly used to investigate hemodynamics in the cardiovascular system, particularly in regions prone to cardiovascular disease such as the carotid artery bifurcation. Despite its potential, significant variability exists across different computational approaches, highlighting the need for systematic solver comparisons. This study provides a comprehensive evaluation of three open-source finite element method (FEM) solvers--SimVascular, FEBio, and FEniCS Oasis--for simulating blood flow in a subject-specific carotid artery model. We conducted a rigorous comparison using a model derived from 4D phase-contrast magnetic resonance imaging (4D Flow MRI), examining solver performance across multiple mesh resolutions. This analysis focused on key hemodynamic metrics, including velocity fields, time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), and WSS topology. By maintaining identical meshes, boundary conditions, and post-processing methods, we isolated solver-specific characteristics while focusing on high-resolution mesh refinements. All solvers demonstrated similar capability in representing the 4D-Flow MRI data. Notably, all solvers consistently identified critical hemodynamic regions, such as flow disturbance zones in the carotid sinus. Mesh convergence analysis showed the ability of all solvers to achieve converged predictions at relatively lower mesh resolutions. The computational time was also compared across the three solvers. While demonstrating the capabilities of each solver in predicting physiologically relevant hemodynamic patterns, our study underscores the utility of open-source solver for high-fidelity hemodynamic predictions.

This study systematically investigates the complex nonlinear rheological behavior of magnetorheological fluids (MRFs) and greases (MRGs) through comparative experiments under two shear modes (steady-state shear and large-amplitude oscillatory shear) at room temperature. Results demonstrate that during steady-state shear tests, the apparent viscosity of both materials decreases with the increasing shear rate, exhibiting shear-thinning behavior at high shear rates that aligns with the Herschel–Bulkley constitutive model. Throughout the logarithmically increasing shear rate range, the viscosity and shear stress of MRF consistently exceed those of MRG. Under low-frequency, large-amplitude oscillatory shear (LAOS) conditions, both materials display pronounced viscoelasticity and hysteresis. At higher current levels, the maximum shear stress of MRF surpasses MRG, but its hysteresis loops exhibit reduced smoothness. The Bouc–Wen model accurately characterizes the nonlinear hysteresis of both materials, with model parameters successfully identified via a genetic algorithm. This work establishes a universal framework for the dynamic mechanical response mechanisms of magnetorheological materials, providing theoretical guidance for designing and predicting the performance of smart damping devices.

Introduction: In repaired tetralogy of Fallot (rToF), asymmetric remodeling of the pulmonary arteries (PA) leads to branch-specific hemodynamic changes. Geometric factors such as curvature influence wall shear stress (WSS) patterns, with distinct effects between the left (LPA) and right pulmonary arteries (RPA). Oscillatory shear index (OSI), which quantifies directional changes in WSS over the cardiac cycle, is a key marker of disturbed flow. This study investigates how curvature and other geometric factors influence hemodynamics in these two branches. Hypothesis: We hypothesize that geometric features influence PA hemodynamics in a branch-specific manner, with curvature having a stronger association with shear-related metrics in certain regions compared to others. Methods: Patient-specific PA models (n = 22) were reconstructed from cardiac magnetic resonance imaging, and computational fluid dynamics simulations were performed under steady and pulsatile flow conditions with patient-derived boundary conditions. Geometric parameters, including curvature and tortuosity, and hemodynamic metrics, including time-averaged WSS and OSI, were quantified. Spearman correlations assessed branch-specific relationships. Results: In the LPA, curvature showed a strong positive correlation with time-averaged WSS (ρ = 0.56, p = 0.006) and a negative correlation with OSI (ρ = -0.52, p = 0.013), indicating that higher curvature segments exhibit more unidirectional, high-shear flow (Figures 1 and 2) . In contrast, RPA curvature did not correlate significantly with any of the measured hemodynamic variables (all p > 0.28). The LPA curvature was significantly greater than the RPA curvature (p = 0.015). Tortuosity did not show significant correlations with hemodynamics in either branch (p > 0.17), suggesting that curvature is the dominant geometric modulator of wall shear stress (Table 1) . Conclusions: The LPA’s curvature-dependent hemodynamics characterized by significant time-averaged WSS and OSI patterns contrast with the RPA’s lack of such correlations. Anatomically, the RPA’s straighter anatomy minimizes flow disruption whereas the LPA curvature increases flow disruption. This study’s results align with prior studies showing sharper angulation in the LPA post-repair, promoting flow acceleration. Clinically, these findings highlight the importance of branch-specific geometric and hemodynamic assessments in rToF follow-up.

Introduction: Concave supra-aortic branched stent-graft (CSBSG) system offers a new option for managing aortic arch pathologies. However, therapeutic efficacy and appropriate implantation regimen of the innovative technique remain unclear. Aims: This study aims to quantify hemodynamic outcomes to assess therapeutic efficacy of CSBSG and then to investigate patient-specific optimization scenarios for further improving CSBSG performance. Methods: Numerical simulations are conducted via CTA datasets from first-in-human cases both before and after CSBSG implantation. Boundary conditions are obtained through three-element Windkessel model. Optimizations on concave degree (angle α) of CSBSG are analyzed in scenarios with patient-specific aortic diameter. Results: Results show that CSBSG insertion can effectively maintain supra-aortic branches blood flow, and will not significantly influence pressure in ascending aorta (AA) and hemodynamic environments whether postoperative blood pressure is normotensive or hypertensive (from 120/80 to 180/140 mmHg). Larger concave angle improves supra-aortic branches perfusion, but also increases pressure and oscillatory shear index in AA. More notable variations are found in patients treated by CSBSG with α ranging from 150° to 180° than from 120° to 150°. Additionally, effects of CSBSG implantation on hemodynamic parameters, e.g., time-averaged wall shear stress, are more pronounced in patients with smaller aortic diameters compared to those with larger diameters. Patients who have (i) larger AA and descending aorta (DA) diameters or (ii) smaller diameter differences between AA and DA, exhibit lower AA pressure, supra-aortic branches perfusion and total energy loss after CSBSG deployment compared with others. Conclusion: Results obtained can provide theoretical foundation in assessing CSBSG outcomes and guiding stent-graft design and determination.

Structural evolution of alginate/calcium β-hydroxy-β-methylbutyrate hydrogel based on nonlinear rheology.

Hemodynamics significantly impact the biology of endothelial cells (ECs) lining the blood vessels. ECs are exposed to various hemodynamic forces, particularly frictional shear stress from flowing blood. While physiological flows are critical for the normal functioning of ECs, abnormal flow dynamics, known as disturbed flows, may trigger endothelial dysfunction leading to atherosclerosis and other vascular conditions. Such flows can occur due to sudden geometrical variations and vascular abnormalities in the cardiovascular system. In the current study, a microfluidic system was used to investigate the impact of different flow conditions (i.e, normal vs. disturbed) on ECs in vitro. We particularly explored the relationship between specific flow patterns and cellular pathways linked to oxidative stress and inflammation related to atherosclerosis. Here, we utilized a 2D cell culture perfusion system featuring an immortalized human vascular endothelial cell line (EA.hy926) connected to a modified peristaltic pump system to generate either steady laminar flows, representing healthy conditions, or disturbed oscillatory flows, representing diseased conditions. EA.hy926 were exposed to an oscillatory flow shear stress of 0.5 dynes/cm2 or a laminar flow shear stress of 2 dynes/cm2 up to 24 h. Following flow exposure, cells were harvested from the perfusion chamber for quantitative PCR analysis of gene expression. Reactive oxygen species (ROS) generation under various shear stress conditions was also measured using DCFDA/H2DCFDA fluorescent assays. Under oscillatory shear stress flow conditions (0.5 dynes/cm2), EA.hy926 ECs showed a 3.5-fold increase in the transcription factor nuclear factor (NFκ-B) and a remarkable 28.6-fold increase in cyclooxygenase-2 (COX-2) mRNA expression, which are both proinflammatory markers, compared to static culture. Transforming growth factor-beta (TGFβ) mRNA expression was downregulated in oscillatory and laminar flow conditions compared to the static culture. Apoptosis marker transcription factor Jun (C-Jun) mRNA expression increased in both flow conditions. Apoptosis marker C/EBP homologous protein (CHOP) mRNA levels increased significantly in oscillatory flow, with no difference in laminar flow. Endothelial nitric oxide synthase (eNOS) mRNA expression was significantly decreased in cells exposed to oscillatory flow, whereas there was no change in laminar flow. Endothelin-1 (ET-1) mRNA expression levels dropped significantly by 0.5- and 0.8-fold in cells exposed to oscillatory and laminar flow, respectively. ECs subjected to oscillatory flow exhibited a significant increase in ROS at both 4 and 24 h compared to the control and laminar flow. Laminar flow-treated cells exhibited a ROS generation pattern similar to that of static culture, but at a significantly lower level. Overall, by exposing ECs to disturbed and normal flows with varying shear stresses, significant changes in gene expression related to inflammation, endothelial function, and oxidative stress were observed. In this study, we present a practical, optimized system as an in vitro model that can be employed to investigate flow-associated diseases, such as atherosclerosis and aortic aneurysm, thereby supporting the understanding of the underlying molecular mechanisms.

Cardiovascular diseases, particularly atherosclerosis, remain the leading cause of mortality worldwide. Atherosclerosis is caused by a buildup of plaque in arteries such as the coronary arteries. The main branch (MB) of coronary bifurcations is a common location where atherosclerotic plaque accumulates, often necessitating stenting procedures. However, MB stenting carries a significant risk of side branch occlusion (SBO), known as a complication with irreversible clinical consequences. This study investigates the effective factors on SBO during MB stenting using a structural and hemodynamic modeling framework. To conduct this modeling, patient-based geometries experienced SBO were reconstructed to simulate balloon inflation in the MB, followed by computational fluid dynamics analysis of pre-stenting hemodynamic parameters using experimentally validated flow conditions. Key geometric and pathological factors, including bifurcation angle (BA), MB stenosis severity (MS), free side branch diameter (SD), and plaque morphology (MP), were systematically varied to assess their impact on the risk of SBO. The simulations revealed that narrow BA and higher MS contribute to deformation of the bifurcation and promote disturbed flow, characterized by enlarged recirculation zone, elevated oscillatory shear index, and enlarged regions of negative period of wall shear stress. In contrast, eccentric plaques (MP) and larger SD can preserve side branch patency by mitigating structural deformation. The results revealed that investigating geometric and pathological factors, as well as hemodynamic parameters, could predict the risk of SBO. The proposed approach can support better-informed decision-making, guide the planning of interventional strategies, and potentially improve long-term procedural outcomes.

Unveiling the structural build-up 3D printable cement-based materials: From small amplitude oscillatory shear (SAOS) to extensional (SAOE) rheological workflows

Influence of wet-type grinder-treated okara on gas retention, specific volume, and crumb characteristics of rice flour bread.

The morphology on the large amplitude oscillatory shear rheological behaviors of hydrocarbon-based gel fuels: A case of study for spherical and flake aluminum particles

Atherosclerosis preferentially develops at arterial bifurcations where the endothelial cells are constantly exposed to disturbed flow, and sustained oscillatory shear stress (OSS) triggers endothelial inflammation. The mechanosensitive transcriptional coactivator YAP plays a critical role in disturbed flow-induced endothelial inflammation. Our recent studies show that disturbed flow upregulates the expression of the mechanosensor 5-HT1B. In this study, we investigated the molecular mechanisms underlying OSS-induced 5-HT1B upregulation in vivo and in vitro. Disturbed flow was induced in mice by partial carotid ligation. In vitro experiments were conducted in human aortic endothelial cells (HAECs) subjected to oscillatory shear stress using an ibidi flow system. We showed that oscillatory shear stress significantly upregulated the expression of 5-HT1B in HAECs via activation of YAP, while knockout of YAP significantly reduced this upregulation. We demonstrated that YAP directly regulated the expression of HTR1B via binding to its promoter region. Inhibition of 5-HT1B using its antagonist SB-216641 impeded YAP nuclear localization and endothelial activation in HAECs. We verified that a 5-HT1B-YAP loop was also activated in atherosclerotic arteries of ApoE-/- mice. Endothelium-specific overexpression of YAP exacerbated atherosclerosis. Moreover, endothelium-specific knockout of 5-HT1B or YAP inhibited disturbed flow-induced endothelial inflammation and plaque formation in ApoE-/- mice. Taken together, the 5-HT1B-YAP positive feedback loop amplifies the pro-atherogenic effect of disturbed flow. We suggest that targeting 5-HT1B-YAP loop holds promise as a novel therapeutic strategy for atherosclerotic diseases.

O/W/O emulsion gel-based fat analogue for encapsulating flavor substances: rheological properties and personalized 3D printing.

Viscosupplementation is a widely used treatment for osteoarthritis, aiming to restore the viscoelastic properties of synovial fluid and improve joint function. While hyaluronic acid (HA), BDDE-crosslinked hyaluronic acid (BDDE-HA), and polynucleotide (PN) have been studied individually, the rheological properties of their mixtures remain insufficiently explored. This study investigates the viscoelastic characteristics of PN/HA and PN/BDDE-HA blends through rheological evaluations, including simple shear tests, oscillatory shear tests, and 3-interval thixotropy tests. Results indicate that BDDE-HA maintains high viscosity over a range of shear rates, whereas PN exhibits viscosity loss at high shear rates. PN/HA exhibits synergistic structural recovery properties, consistent with clinical findings suggesting improved efficacy compared to individual components. PN/BDDE-HA exhibits improved viscoelastic behavior but prolonged structural recovery. These findings highlight the importance of comprehensive rheological analysis in understanding viscosupplement formulations and their potential clinical implications. This study provides fundamental data to support future clinical research on PN/BDDE-HA as a novel viscosupplement.

ABSTRACT This study investigates the effect of processing parameters on the dispersion quality of carbon nanotube (CNT) within poly(butylene adipate‐co‐terephthalate) (PBAT) matrix and the corresponding rheological behavior, electrical conductivity, dielectric properties, and electromagnetic interference shielding effectiveness (EMI‐SE). Neat PBAT and nanocomposites containing 1, 3, and 5 wt% CNT were prepared using an internal melt mixer with varying processing temperatures and screw speeds. Small amplitude oscillatory shear rheological analysis revealed that an increase in processing temperature resulted in a more significant increase in complex viscosity and storage modulus at low frequencies reflecting a better CNT dispersion and the formation of a stronger network. Higher mixing speeds also facilitated CNT dispersion more effectively; although further increases could cause the mechanical degradation of PBAT molecules and CNTs breakage. Scanning electron microscopy analysis confirmed the better and more uniform CNT dispersion when the nanocomposites were processed at higher temperatures and mixing speeds. The changes in electrical conductivity, dielectric permittivity, and EMI‐SE of the nanocomposites were consistent with the melt rheological results confirming a symbiotic correlation between these characteristics. Nanocomposites with 5 wt% CNT revealed DC conductivity and EMI‐SE values of about 10 −7 S/cm and 35–38 dB, respectively, when processed at 150°C and 100 rpm. These values, however, reached about 10 −3 S/cm and 44–50 dB, respectively, when nanocomposites were prepared at 190°C and 200 rpm. Under this preparation condition, the onset of rheological and electrical conductivity percolation thresholds was estimated at CNT contents of about 0.18 and 0.45 wt%, respectively. A higher processing temperature (190°C) and increased mixing speed (200 rpm) were found to be critical in achieving uniform CNT dispersion and enhancing the multifunctional properties of the nanocomposites.

Sodium glucose co-transporter 2 inhibitor empagliflozin prevents endothelial dysfunction induced by oscillatory shear stress.

Abstract In this work, we have studied the viscoelastic behavior of chemically and physically crosslinked Poly(vinyl alcohol) (PVA) hydrogels near the critical gel point (GP) as well as further away from it, by means of small amplitude (SAOS) and large amplitude (LAOS) oscillatory shear experiments. Chemical crosslinking involved covalent bonding by means of glutaraldehyde as a crosslinker, while physical crosslinking was induced by freeze–thaw cycles. SAOS data analysis allowed evaluation of critical parameters such as the critical relaxation exponent n, gel strength S, and equilibrium modulus Ge, based on the dynamic self-similarity and fractal network structures at the GP. LAOS rheological data analysis showed that the chemically crosslinked system exhibited moderate strain-dependance due to the permanent covalent bonds, whereas the physically crosslinked system displayed significant strain-dependent nonlinearity due to strain dependent interactions at the crosslink entities. LAOS experiments, supported by Chebyshev coefficients and Lissajous-Bowditch plots, highlighted pronounced differences in nonlinear responses, underscoring the influence of crosslinking mechanisms on the network rheological behavior. The findings establish LAOS as a powerful tool for differentiating polymeric network structures, providing insights beyond those attained by conventional linear rheology.