Shear Conditions Research Articles

Abstract 4137045: Sustained Anti-Thrombotic Efficacy of CS585, a Novel Prostacyclin Receptor Agonist, Demonstrates Therapeutic Potential

The formation of occlusive thrombi resulting in myocardial infarction or stroke present a significant challenge for the healthcare community. Activation of the prostacyclin (IP) receptor has been shown to decrease platelet reactivity, however current IP agonists lack a sustained effect in the blood. We have developed CS585, an IP receptor agonist with sustained anti-thrombotic effects in the blood, which could represent a novel prevention strategy in targeting thrombosis. We sought to assess the anti-thrombotic efficacy and pharmacodynamic stability of IP agonists CS585, iloprost and selexipag, in both ex vivo and in vivo models. We evaluated the timeframe of effect of CS585, iloprost, and selexipag in mice following a single IV dose. Inhibition of thrombus formation was measured ex vivo in whole blood under arterial shear rates. In vivo , CS585, iloprost, or selexipag, were administered prior to labeling of platelets and fibrin. Thrombus formation at the site of injury was measured using the cremaster arteriole injury thrombosis assay. CS585 administered to mice prior to blood draw decreases platelet adhesion and blood clot formation under arterial shear conditions. These effects are observed up to 24 hours post-administration; however, the effects of iloprost and selexipag return to pre-treatment levels by 24 hours. In vivo , mice administered iloprost or selexipag demonstrated a decrease in platelet accumulation and fibrin formation, however the effects were abrogated post-administration by 10 minutes and 4 hours, respectively. Administration of CS585, however, demonstrated sustained inhibition of thrombus formation at the site of injury, with inhibitory effects observed at 18 hours post-administration. We have used both in vivo and ex vivo models to demonstrate the anti-thrombotic efficacy of IP receptor agonists. Our results suggest that CS585, a novel IP receptor agonist, sustainably inhibits platelet activation and clot formation for extended periods, in contrast to existing alternatives. This demonstrates a significant improvement in the pharmacodynamic effects of IP receptor agonists in the blood, highlighting CS585 as a novel anti-platelet therapeutic with the potential to treat thrombotic diseases.

Effect of Particle Shape on Cyclic Shear Behavior of Granular Mixtures–Geogrid Interface

The cyclic shear stiffness and damping ratio of angular and round particle geogrid interfaces is of much concern in reinforcement structure seismic analysis. In this study, various component percentages of crushed limestone and spherical granular medium mixtures were used to investigate the role of particle regularity in static and cyclic direct shear tests. The test results revealed that an increase in the proportion of round particles decreased cyclic shear strength and volume change. The phenomenon of shear softening was observed with a high amplitude of shear displacement when the proportion of round particles was increased in the mixture. As the percentage of round particles increased, the maximum interface shear stiffness decreased significantly from, 39.69 to 28.28 MPa/m, but a reverse trend in the maximum damping ratio was observed, from 0.308 to 0.37. The effect of cyclic shear history and proportion of round particles on interface strength parameters was also analyzed. A linear regression model was fitted to the data for quantifying the relationship between the proportion of round particles and friction angle. The results suggest that different percentages of round and angular particles can produce varying degrees of particle interlock between aggregate and geogrid, influencing the macro-mechanical behavior of the reinforced soil interface.

Experimental and numerical investigation on the effect of process parameters on joint strength and failure behavior of self-piercing riveted steel/aluminium hybrid joints

To further improve the joint strength and identify the potential failure behavior of self-piercing riveted (SPR) steel/aluminium hybrid joints under shear and cross-tension loading conditions, a simplified 2D-to-3D simulation process chain is proposed. The finite element models (FEM) for the failure process of SPR joints are established in LS-DYNA and verified against experimental results. The effects of rivet strength, sheet material and thickness, and riveting direction on the joint strength and failure behavior of SPR joints are investigated. The results show that when the rivet strength is less than 1.3 GPa, increasing the rivet strength can improve the joint strength of AS joints under shear load and SA joints under cross-tension load. The joint strength of two types of SPR joints increases gradually and then decreases with an increase in thickness ratio Rt. When the steel/aluminium sheet thickness ratio Rsa exceeds 1.47, the aluminium-to-steel direction should be chosen. Increasing material strength can improve the joint strength of two types of SPR joints, while their sensitivities to the material strength vary under different loading conditions. The sheet material, sheet thickness, and riveting direction can change the failure behavior of the joints, while the rivet strength does not alter the failure behavior. This work contributes to understanding the mechanism of joint strength improvement and enhances riveting quality in industrial practice.

Machine learning-based design of double corrugated steel plate shear walls

PurposeIn this study, machine learning (ML) algorithms were employed to predict the shear capacity and behavior of DCSWs.Design/methodology/approachIn this study, ML algorithms were employed to predict the shear capacity and behavior of DCSWs. Various ML techniques, including linear regression (LR), support vector machine (SVM), decision tree (DT), random forest (RF), extreme gradient boosting (XGBoost) and artificial neural network (ANN), were utilized. The ML models were trained using a dataset of 462 numerical and experimental samples. Numerical models were generated and analyzed using the finite element (FE) software Abaqus. These models underwent push-over analysis, subjecting them to pure shear conditions by applying a target displacement solely to the top of the shear walls without interaction from a frame. The input data encompassed eight survey variables: geometric values and material types. The characterization of input FE data was randomly generated within a logical range for each variable. The training and testing phases employed 90 and 10% of the data, respectively. The trained models predicted two output targets: the shear capacity of DCSWs and the likelihood of buckling. Accurate predictions in these areas contribute to the efficient lateral enhancement of structures. An ensemble method was employed to enhance capacity prediction accuracy, incorporating select algorithms.FindingsThe proposed model achieved a remarkable 98% R-score for estimating shear strength and a corresponding 98% accuracy in predicting buckling occurrences. Among all the algorithms tested, XGBoost demonstrated the best performance.Originality/valueIn this study, for the first time, ML algorithms were employed to predict the shear capacity and behavior of DCSWs.

Co-vulcanization of natural rubber and Eucommia ulmoides gum for mediation of the nonlinear rheology behaviors

Co-vulcanization of natural rubber (NR) and high-moduli Eucommia ulmoides gum (EUG) is promising while the reduction in crystallinity of crosslinked EUG is adverse for developing high-performance materials. Proposed herein is a novel method to prepare high-strength and high-stretchability NR/EUG vulcanizates with rapid vulcanization of EUG into slightly crosslinked particles, followed by further vulcanization of NR to form crosslinked matrix network. Deep eutectic solvents (DESs) are employed to facilitate the vulcanization of EUG during its blending with NR. The two-step vulcanization results in vulcanizates exhibiting superior mechanical properties under shear, tensile, and compressive conditions, significantly exceeding those of vulcanizates prepared by traditional processing methods. The reinforcement mechanism is elucidated by controlling thermomechanical coupling conditions and is supported by comprehensive structural characterizations. It is suggested that the EUG crystalline regions, maintained through the special processing method, work in conjunction with the stress-induced crystallization of the matrix to enhance the vulcanizates, nearly doubling the deformation stress at 800% strain. The crystalline regions can mediate the deformation stress during shear and compression and weaken nonlinear rheological behavior. The established structure-performance relationship is guidable for preparing high-performance NR/EUG blend vulcanizates.

Permanent deformation and particle crushability of calcareous sands under cyclic traffic-induced loadings through simple shear apparatus

This study focuses on investigating permanent deformations, encompassing normal and shear strains, of calcareous sandy soils subjected to drained cyclic traffic-induced loadings. The investigation utilizes a Simple Shear (SS) apparatus allowing for variations in both normal and shear stress components over each cycle and incorporates Principal Stress Rotation (PSR), a feature not replicable in conventional cyclic uniaxial triaxial tests which is the key aspect of this research. The study also accounts for the harmonically changing the effective horizontal stress resulting from cyclic variations of effective vertical stress, conducted under a horizontally constrained boundary condition with zero lateral strain. A series of drained cyclic simple shear experiments is carried out, implementing a heart-shaped stress path, encompassing up to 1000 cycles. The objective of the study is to analyze permanent normal and shear deformations, along with associated total particle crushing, using both sieving analyses and 2D image processing of particles. The study also evaluates the impact of an initial static shear stress originating from the longitudinal slope of roads. The findings highlight the influences of induced cyclic amplitudes of stress components, principal stress and strain rate rotation, and initial static shear stress on the development of permanent strains. Furthermore, the research characterizes particle crushability in terms of total crushability over such loading, examining its dependency on relative density and variations in both shear and normal stress components.

Simulation of unsteady ice accretion on horizontal axis wind turbine blade sections in turbulent wind shear condition

This study presents a comprehensive simulation approach to quantify power losses in horizontal axis wind turbines under environmental icing conditions. It investigates how wind shear and turbulence affect a 2.5 MW wind turbine's performance, particularly under ice accretion. Turbulence intensity, ranging from 1% to 20%, impacts the relative flow fluctuations and angle of attack on the blade sections, influencing the aerodynamic penalty ratio. The incoming wind speed and the flow angle at various blade sections were determined using the unsteady blade element momentum method, considering vortex induction effects and Prandtl and Glauert corrections. For ice accretion analysis, a fully unsteady simulation of computational grid motion due to ice accretion was performed, along with the solution of the multiphase flow of water dispersed particles in cold air, derived from the psychrometric chart. The findings highlight the significant impact of the incoming turbulent wind fluctuations on the dispersion of the ice shape formed at sections corresponding to their radial position on the blade according to the momentary angle of attack fluctuations. The formation of ice profiles along the blade has led to a subsequent degradation in the aerodynamic efficiency of the blade sections, which is directly proportional to the escalation in turbulence intensity. This phenomenon leads to a continual reduction in the power output of the wind turbine. This research provides valuable insights into the performance of wind turbines under icing conditions in real wind fluctuations.

Soil fluidisation induced by fine particles migration: Insights from the Shenzhen 2015 landfill landslide

Naturally completely decomposed granite (CDG) soil typically exhibits strain-hardening behavior under undrained shear conditions. Nevertheless, flow-type landslides are not uncommon in CDG landfills. This paper endeavors to address the observed contradiction by conducting a case study of the 2015 Shenzhen landslides. Based on field investigations, we propose a hypothesis for the initiation and evolution of flow-type landslides in CDG landfill slopes, termed ‘clay particle argillization, mud-water migration, and static liquefaction’. This hypothesis was verified by element-scale internal erosion tests and triaxial tests, and further elucidated by microscale particle analysis. It was observed that the internal erosion-induced removal of plastic fine particles and retention of low-plasticity fine particles from CDG soil promotes the sliding and reorganization of coarse granules under shear stress, thereby increasing the soil's susceptibility to fluidization under undrained conditions. The proposed hypothesis and experimental findings provide new insights into the instability and subsequent extensive runout of CDG landfills and analogous broadly graded landslides.

The durability of viscosity reduction of magnetically treated waxy crude oil

Magnetic treatment is a method for improving the cold flowability of waxy oils. Previous studies have predominantly focused on the viscosity reduction resulted from the treatment, with the durability of the magnetic effect neglected, which is crucial for pipeline transportation of the treated crude oil. Therefore, this study focuses on the durability and its mechanism of the magnetic effect of a waxy crude oil under static, low shear, and high shear conditions. A viscosity reduction of 15.7% was achieved under the magnetic treatment condition of the magnetic treatment temperature at 52 °C, magnetic field strength at 0.1 T, and a duration of 1 min. However, the magnetic effect gradually diminished with time elapsing and disappeared in 9 h under static conditions. Shear was found to be beneficial to the preservation of the effect, and a correlation between the viscosity of the sheared treated-oil and the energy dissipation of the shear was found. Microscopic observations, impedance measurements, and x-ray diffraction analysis revealed that exposure to a magnetic field might disperse the charged particles, i.e., resins and asphaltenes, in the crude oil, facilitating their adsorption on the wax particle surfaces, thus enhancing electrostatic repulsion among wax particles and resulting in viscosity reduction. The desorption of the adsorbed resins and asphaltenes from the wax particles and reaggregation lead to the gradual diminishment of the viscosity reduction. Shear might inhibit this reaggregation and thus contribute to the durability of the viscosity reduction.

Influence of Basalt Fiber Morphology on the Properties of Asphalt Binders and Mixtures.

Basalt fiber (BF) has been proven to be an effective additive for improving the properties of asphalt mixtures. However, the influence of basalt fiber morphology on the properties of asphalt binders and mixtures remains inadequately explored. In this study, chopped basalt fiber (CBF) and flocculent basalt fiber (FBF) were selected to make samples for testing the influence of the two types of basalt fibers on asphalt materials. Fluorescence microscopy was used to obtain the dispersion of fiber in asphalt binders. Then, a temperature sweep test and a multiple stress creep recovery (MSCR) test were carried out to appraise the rheological characteristics of the binder. Moreover, the performance of the fiber-reinforced asphalt mixture was evaluated by a wheel tracking test, a uniaxial penetration test, an indirect tensile asphalt cracking test (IDEAL-CT), a low-temperature bending test, a water-immersion stability test, and a freeze-thaw splitting test. The results indicate that the rheological behavior of asphalt binders could be enhanced by both types of fibers. Notably, FBFs exhibit a larger contact area with asphalt mortar compared to CBFs, resulting in improved resistance to deformation under identical shear conditions. Meanwhile, the performance of the asphalt mixture underwent different levels of enhancement with the incorporation of two morphologies of basalt fiber. Specifically, as for the road property indices with FBFs, the enhancement extent of DS in the wheel tracking test, that of RT in the uniaxial penetration test, that of the CTindex in the IDEAL-CT test, and that of εB in the low-temperature trabecular bending test was 3.1%, 6.8%, 15.1%, and 6.5%, respectively, when compared to the CBF-reinforced mixtures. Compared with CBFs, FBFs significantly enhanced the elasticity and deformation recovery ability of asphalt mixtures, demonstrating greater resistance to high-temperature deformation and a more pronounced effect in delaying the onset of middle- and low-temperature cracking. Additionally, the volume of the air void for asphalt mixtures containing FBFs was lower than that containing CBFs, thereby reducing the likelihood of water damage due to excessive voids. Consequently, the moisture susceptibility enhancement of CBFs to asphalt mixture was not obvious, while FBFs could improve moisture susceptibility by more than 20%. Overall, the impact of basalt fibers with different morphologies on the properties of asphalt pavement materials varies significantly, and the research results may provide reference values for the choice of engineering fibers.

Selection of the optimal formulation of the biopolymer system for the stimulation of productive formations

The object of study in this paper is the biopolymer system «X» – a complex composition that includes a biopolymer, salts and a thermal stabiliser intended for use in drilling fluids at high temperatures. The components of the formulation include complex reagent «X» for regulating structural, mechanical, rheological and filtration properties, as well as inhibitors (sodium and potassium chloride) and filler. Components of the biopolymer system (sodium chloride, organo-mineral colmatant thermal stabiliser) increase its thermal stability. One of the most problematic areas is the mechanism of sodium chloride's thermal stabilising effect. It is associated with an increase in the overall mineralisation of the drilling mud, which leads to a certain conformation of biopolymer molecules, accelerates gelation processes and counteracts the temperature dilution of the system. The results obtained can be explained as follows: – an increase in the concentration of sodium chloride leads to an increase in the ionic strength of the solution, which contributes to a change in the conformation of biopolymer molecules, enhancing intermolecular interactions and, as a result, increasing the viscosity and stability of the system; – the organo-mineral colmatant heat stabiliser promotes the formation of a filtration crust on the well walls, which prevents fluid loss and reduces rock permeability; – all components of the system interact with each other, affecting the properties of the solution. The optimum ratio of components allows achieving the required rheological characteristics and ensuring the stability of the system at high temperatures. As a result of processing the information on technologies for tapping productive horizons, the disadvantages and advantages of each of them were noted. The existing drilling fluid systems used to tap productive horizons at high temperatures were considered. However, more attention was paid to the selection of a new optimal formulation of the biopolymer system, in accordance with the specified rheological and structural and mechanical properties for further implementation in practice. This ensures the possibility of obtaining predictive parameters of the drilling mud. The proposed system has a number of advantages over similar ones, namely: – the system retains its properties at high temperatures; – the system provides the required values of viscosity, filtration and static shear stress; – due to the use of an optimal formulation, high efficiency is achieved at a relatively low cost.

Shear behavior at the interface of rough surfaces and cohesive soils under axial loading

Foundation elements with rough (textured) surfaces mobilize larger interface shear resistance than ones with conventional smooth or random rough surfaces when sheared against soils under monotonic loading. The overall performance of foundation elements such as piles supporting offshore wind turbines, suction caissons supporting tidal energy converters, soil nails, and soil anchors installed in cohesive soils could be enhanced through utilizing rough (textured) surfaces to resist applied static and/or cyclic loading. This paper describes the shear behavior of smooth and rough (textured) surfaces in kaolinite clay and kaolinite clay-sand mixture soils under static and cyclic axial loading. The experimental investigation presented herein consists of a series of interface shear tests performed on 3D printed rough (textured) surfaces and a 3D printed smooth reference surface utilizing the Cyclic Interface Shear Test system. The paper includes a description of the interface testing system components, cohesive soil specimens’ preparation procedure, smooth and rough (textured) surfaces details, testing procedure, and results of static and cyclic tests. Test results indicate that kaolinite clay-sand mixture soil mobilized larger static and post-cyclic interface shear resistance and volume contraction relative to kaolinite clay soil when sheared against the smooth reference surface. When tested against rough (textured) surfaces with variable asperity height, larger shear resistance was mobilized and larger soil dilation greater than that mobilized by the reference untextured surface in both soils. The results also indicate rough (textured) surfaces exhibited a prevalent frictional anisotropy increases with asperity angle and height in cohesive soils, the surfaces mobilized larger shear resistance and volume change in one direction (i.e., against the asperity right-angled side) than the other direction (i.e., along the asperity inclined side).

Lipopolysaccharide from Proteus mirabilis Slows Platelet Plug Formation in Human Whole Blood

Platelets are well known for their role in hemostasis. Additionally, platelets play a crucial role in immune and inflammatory responses. Toll-like receptors (TLRs) can mediate bacterial interactions during infection, triggering platelets to initiate an inflammatory response. TLR-4 receptors enable direct interactions between platelets and the bacterial lipopolysaccharide (LPS) endotoxin. The aim of this study was to assess platelet plug formation in response to LPS from Proteus mirabilis. Human whole blood was treated with varying concentrations of LPS over a range of incubation times. Then, platelet plug formation time was measured, under high shear conditions using the platelet function analyzer PFA-100, as aperture closure time (CT). The addition of either 2 or 10 µg/mL of LPS to 80% whole blood significantly prolonged the CTs even in the absence of preincubation (p = 0.028 or p = 0.049, respectively). With added preincubation of LPS with whole blood, the measured CTs were further prolonged. If the preincubation time was set to 35 min, then even the addition of 0.2 µg/mL of LPS resulted in significant CT prolongation (p < 0.001). Taken together, the platelet plug formation in the presence of collagen/ADP is significantly prolonged by the presence of LPS in a concentration and preincubation time-dependent manner. Exposure to P. mirabilis LPS reduces the platelet aggregation response in human whole blood.

A Microfluidic Design for Quantitative Measurements of Shear Stress-Dependent Adhesion and Motion of Dictyostelium discoideum Cells

Shear stress plays a crucial role in modulating cell adhesion and signaling. We present a microfluidic shear stress generator used to investigate the adhesion dynamics of Dictyostelium discoideum, an amoeba cell model organism with well-characterized adhesion properties. We applied shear stress and tracked cell adhesion, motility, and detachment using time-lapse videomicroscopy. In the precise shear conditions generated on-chip, our results show cell migration patterns are influenced by shear stress, with cells displaying an adaptive response to shear forces as they alter their adhesion and motility behavior. Additionally, we observed that DH1-10 wild-type D. discoideum cells exhibit stronger adhesion and resistance to shear-induced detachment compared to phg2 adhesion-defective mutant cells. We also highlight the influence of cell density on detachment kinetics.

Clustering of tropical species through multivariate analysis of the bonding properties of edge-glued panels (EGP)

Tropical woods have high added value, and the use of waste for panel production is an initiative to add more value to this material, typically consisting of various species. The use of raw materials from tropical solid wood waste in the Amazon region contributes to the reduction of carbon emissions associated with the burning of this material. In this context, this study aimed to cluster species based on the bonding properties of Amazonian woods by applying multivariate analysis. The apparent density 12% and strength of finger joint and edge-glued joints of Cedrela odorata, Enterolobium schomburgkii, Erisma uncinatum and Qualea paraensis was evaluated which were joined in homogeneous and hybrid configurations with the adhesives PVA and EPI, as spreading rate of 180 g/m2. The treatments were compared by multivariate analysis of variance and discriminant analysis. The discrimination of species and combinations based on wood density (low, medium, and high) revealed that this is the most important characteristic for grouping different species that make up tropical hardwood waste for the production of EGP panels. In practice, the separation of species into groups according to wood densities can contribute to a better definition of the indications for use of edge glued panels of each density class, and assertive targeting for applications according to the strength ranges required. In the static bending, parallel tensile and shear tests all species and their combinations met the minimum requirements normative, indicating the approval of species and combinations studied for the production of EGP panels.

Ethanolamine-modified gel electrolyte of zinc ion battery

The rapid growth of wearable electronic devices has spurred the development of flexible energy storage systems. However, the limitations of conventional rigid commercial batteries have hindered the advancement of wearable technology. Consequently, the development of stable, safe, highly flexible, and cost-effective flexible batteries has become a key focus in current battery research. Herein, we introduce a novel multifunctional flexible Prussian Blue–zinc battery utilizing a PVA-ZnCl₂ polymer gel electrolyte (EGPE) enhanced with ethanolamine (ETA), aimed at addressing the deficiencies of traditional electrolytes in terms of safety and mechanical performance. The Zn||Zn symmetric cell using EGPE electrolyte demonstrated an impressive long-term cycling stability of over 3000 hours at a current density of 0.15 mA cm−2. In contrast, the symmetrical cell using 0.8 M ZnCl2 aqueous electrolyte maintained its stability for only 400 hours. In addition, the prepared flexible zinc Prussian blue device maintained more than 65 % of its initial capacity of the device and its coulombic efficiency was close to 100 % after 400 cycles at an extreme current density of 10 A g−1. Furthermore, flexible device using the EGPE was able to maintain a stable power supply under various bending, torsion, folding and shearing conditions. Such innovative gel electrolyte demonstrated considerable prospects for utilisation in portably equipped devices and energy storage systems.

Small-scale wind fluctuations within melting layers of winter storms: results from WINTRE-MIX

Abstract Investigations into the melting layer (ML) of winter storms have revealed small-scale fluctuations in the horizontal wind that could significantly affect surface precipitation type and the evolution of the ML. Despite previous evidence of such fluctuations, essential questions remain concerning their characteristics and the forces driving them. Therefore, this study characterizes small-scale horizontal wind fluctuations (<1 km in length with perturbation magnitudes < 3 m s−1) and their environments within the ML of winter storms. This analysis uses data from a scanning X-band Doppler radar collected during the Winter Precipitation Type Research Multi-Scale Experiment (WINTRE-MIX), conducted during February and March 2022. We present three case studies where small-scale horizontal wind fluctuations are identified using along-radial and along-azimuthal radial velocity perturbations. These cases cover the range of environmental conditions observed during WINTRE-MIX, including: i) a descending ML with change in surface p-type from snow to rain, ii) a steady ML with a surface p-type transition from freezing rain to rain due to surface cold air erosion, and iii) a steady ML with a surface p-type transition from freezing rain to ice pellets due to surface cold air advection. Forcing mechanisms for small-scale wind fluctuations during each case are attributed to static instability, vertically trapped gravity waves, and/or shear instability inferred from rawinsonde data, HRRR analysis, and radar data. Our findings suggest that static instability, gravity waves, and shear instability drive the ML’s small-scale wind fluctuations and may influence surface precipitation-type transitions.

Low shear-induced fibrillar fibronectin: comparative analyses of morphologies and cellular effects on bovine aortic endothelial cell adhesion and proliferation

Wall shear stress (WSS) is a critical factor in vascular biology, and both high and low WSS are implicated in atherosclerosis. Fibronectin (FN) is a key extracellular matrix protein that plays an important role in cell activities. Under high shear stress, plasma FN undergoes fibrillogenesis; however, its behavior under low shear stress remains unclear. This study aimed to investigate the formation ofin vitrocell-free fibrillar FN (FFN) under low shear rate conditions and its effect on bovine aortic endothelial cell behavior. FN (500µg ml-1) was perfused through slide chambers at three flow rates (0.16 ml h-1, 0.25 ml h-1, and 0.48 ml h-1), corresponding to low shear rates of 0.35 s-1, 0.55 s-1, and 1.05 s-1, respectively, for 4 h at room temperature. The formed FN matrices were observed using fluorescence microscopy and scanning electron microscopy. Under low shear rates, distinct FN matrix structures were observed. FFN0.48 formed immense fibrils with smooth surfaces, FFN0.25 formed a matrix with a rough surface, and FFN16 exhibited nodular structures. FFN0.25 supported cell activities to a greater extent than native FN and other FFN surfaces. Our study suggests that abnormally low shear conditions impact FN structure and function and enhance the understanding of FN fibrillogenesis in vascular biology, particularly in atherosclerosis.

Two-species model for nonlinear flow of wormlike micelle solutions. Part II: Experiment

Applications often expose wormlike micelle solutions to a very wide range of shear and temperature conditions. The two-species model presented in Part I [Salipante et al., J. Rheol. 68 (2024)] describes the nonlinear rheology over a wide range of shear rates. Here, we compare the model predictions to measurements using a combination of microcapillary and rotational rheology to measure the viscosity of surfactant solutions across seven decades of shear rate and five decades of viscosity. The effect of temperature is studied between 20 and 60 °C for different surfactant concentrations. Model parameters are determined from both small-amplitude shear measurements and fitting to the nonlinear data. Under shear stress, the model predicts due to hindered combination kinetics that the average micelle length decreases from several micrometers to a few hundred nanometers. At sufficiently high stress, the micelle shear rheology exhibits a transition from entangled wormlike behavior to a dilute rod rheology in agreement with the model. Transient stress-growth measurements exhibit a large overshoot, which is rather well predicted by the model with hindered combination rate. Microcapillary flow birefringence also is adequately predicted by the model, confirming the accuracy of its predicted micelle lengths and exhibiting a marked change in stress-optic response at the transition between entangled polymers and dilute rods. The relaxation of retardance after flow cessation follows model predictions that include micelle-micelle interactions, which are sensitive to the rotational diffusivity and length. These methods can be applied broadly to explore relationships between composition and performance.

Experimental study on the thixotropic strength of the marine soft clay from the Yangtze River estuary

Soft clay in the offshore area of the Yangtze River estuary has been investigated considering its basic physical properties. Forty-five unconfined compressive strength tests were conducted on the remolded marine soft clay to investigate the impacts of curing time T, water content w, plasticity index IP, and clay particle content ρc on the thixotropic static shear strength ratio As of the marine soft clay from the Yangtze River estuary. Results show that the stress–strain curves were primarily strain hardening and strain softening curve types. Unconfined compressive strength qu increased with an increase in T. All specimens with different basic physical properties were capable of thixotropic strength recovery. When T = 0–28 days, As increased rapidly, while for T > 28 days, As of most specimens increased slightly or tended to stabilize. The impacts of w, IP and ρc on As do not follow a consistent pattern, but there is a strong correlation between As and w/wL (wL is the liquid-limit water content). For w/wL < 0.75, As increased with increasing w/wL, whereas for w/wL ≥0.75, As decreased with increasing w/wL. We proposed a simple and widely applicable power function prediction model for the As of the soft clay from the Yangtze River estuary.