Shear Stress Research Articles

Experimental determination of maximum shear stress in Mobius® Breez perfusion microbioreactors and comparative analysis with stirred tank bioreactors

Perfusion processes have experienced increased popularity in recent years due to their ability to sustain high cell densities and productivities in biopharmaceutical production, offering advantages over traditional batch and fed-batch cultivation methods. The Mobius® Breez microbioreactor significantly reduces experimental effort by downsizing the classical volume of perfusion bioreactors to the mL range and thus represents a valuable tool for process development. However, miniaturization has raised questions regarding comparability with traditional bioreactors in terms of the physical environment, such as hydrodynamic shear stress. Therefore, the maximum hydrodynamic shear stress, cultivation performance, and membrane-wall contact were evaluated to elucidate the system's behavior. Findings reveal two distinct operational conditions, distinguished by the presence or absence of membrane-wall contact, resulting in varying levels of hydrodynamic stress. Conditions lacking membrane contact demonstrate stress levels within safe operating thresholds for CHO cells, while those involving membrane contact exceed these thresholds, potentially leading to cell damage. Through the identification of critical frequencies of membrane motion, this study offers insights for optimizing microbioreactor operation and enhancing overall bioprocess efficiency.

Local Morphologic and Hemodynamic Analyses for the Prediction of Abdominal Aortic Aneurysm Rupture Based on Patient-Specific CTA and Computational Modeling.

Extensive research has focused on the evaluation of rupture risks in abdominal aortic aneurysms (AAAs) through comprehensive morphologic and hemodynamic analyses, primarily considering the AAA as a whole entity. This study tried to identify the high-risk rupture sites of AAAs more precisely before the fatal process based on morphologic and hemodynamic analyses at the local segment. Computed tomography angiography of a specific AAA patient was conducted at the follow-up 4 months before rupture, 1 day before rupture, the day of the rupture, and 15 days after endovascular aortic repair. The evolution of local morphology and the hemodynamic characteristics at these critical timepoints were investigated based on patient-specific reconstructions and computational fluid dynamics. The morphologic and hemodynamic parameters of the rupture region vary continuously in the process of AAA development and rupture. The surface area and volume of the rupture segment were gradually enlarged at the follow-up 4 months before rupture (47.33 cm2; 67.35 mL), 1 day before rupture (57.23 cm2; 85.24 mL), and on the day of the rupture (62.41cm2; 104.73ml). A prominent decrease in time-averaged wall shear stress and velocity for the rupture segment is observed. The percentages of the lowest time-averaged wall shear stress (<0.1 Pa) area are increased in the AAA region (20.42%, 33.85%, and 53.00%, separately). The results based on precisely rebuilt geometries for the complete follow-ups of patient-specific computed tomography angiography demonstrate that notable morphologic and hemodynamic evolutions have occurred in the local segment of the AAA, which was further proved at the rupture site. The significant changes occurring at the local segment may provide valuable information for the evaluation of aneurysm rupture risk and locate the most probable site of rupture. Capturing the entire process of AAA rupture through CTA imaging is a rare occurrence in clinical practice. The evolution of morphology and hemodynamic characteristics observed in the illustrated results provides valuable insights for clinicians to monitor the state of AAA from a different perspective. These findings suggest that variations in morphology and hemodynamics within the local segment of the AAA might serve as an alternative approach for predicting the rupture risk of AAA.

Rheological Characteristics of Concrete Mixtures Modified with Urease Additives

Statement of the problem. Rheological characteristics of concrete samples made with the use of various bioadditives are studied. Results. The results of experimental studies of the rheological properties of concrete, taking into account the effect of dietary supplements based on the following strains of bacteria B.subtilis, Ps.aeruginosa, with urease activity, are presented. Conclusions. The values of the cone sediment of concrete mixtures made using various grades of Portland cement were obtained, the values of conditional viscosity were also established, and the limiting shear stress and compressive strength of the obtained concrete cube samples made using urease bioadditives were determined. It was found that the use of dietary supplements leads to a decrease in the conditional viscosity of the mixture by 2 times, as well as to an increase in compressive strength by at least 15 %. Thus, it has been established that bioadditives improve the quality of the bond between the components of concrete, making it more durable and resistant to loads, as well as its rheological characteristics.

Modeling Fibrin Accumulation on Flow-Diverting Devices for Intracranial Aneurysms.

The mechanisms leading to aneurysm occlusion after treatment with flow-diverting devices are not fully understood. Flow modification induces thrombus formation within the aneurysm cavity, but fibrin can simultaneously accumulate and cover the device scaffold, leading to further flow modification. However, the interplay and relative importance of these processes are not clearly understood. A computational model of fibrin accumulation and flow modification after flow diversion treatment of cerebral aneurysms has been developed under the guidance of invitro experiments and observations. The model is based on the loose coupling of flow and transport-reaction equations that are solved separately by independent codes. Interaction or reactive terms account for thrombin production from prothrombin stimulated by thrombogenic metallic wires and inhibition by antithrombin as well as fibrin production from fibrinogen stimulated by thrombin and flow shear stress, and fibrin adhesion to device wires and already attached fibrin. The computational model was demonstrated and tested on idealized vessel and aneurysm geometries. The model was able to reproduce the salient features of fibrin accumulation after the deployment of flow-diverting devices in idealized invitro models of cerebral aneurysms. Namely, fibrin production in regions of high shear stress, initial accumulation at the inflow zone, and progressive occlusion of the device and corresponding flow attenuation. The computational model linking flow dynamics to fibrin production, transport, and adhesion can be used to investigate and better understand the effects that lead to fibrin accumulation and the resulting aneurysm inflow reduction and intra-aneurysmal flow modulation.

Effect of soft magnetic particles content on multi-physics field of magnetorheological composite gel clutch with complex flow channel excited by Halbach array arrangement

In this paper we investigate the influence of soft magnetic particle mass fraction on the multi-physics field of proposed magnetorheological (MR) gel clutch. A novel MR gel clutch with complex cup-shaped gap is described, whose performance is based on the relative placement between Halbach array arrangement and MR gel. Smart MR gel with 40 wt%, 50 wt%, 60 wt%, 70 wt% and 80 wt% of soft magnetic particles used as the transfer medium and Halbach array is adopted as magnetic excitation system. Its magnetic/mechanical analysis is carried out based on Bingham-plastics model using COMSOL Multiphysics software, which takes into account the variation of dynamic viscosity with magnetic flux density. The distribution of the magnetic flux density, shear yield stress, post-yield viscosity, shear stress and torque in the four flow channels during the transition from engagement state to disengagement state are obtained and analyzed in detail. Multi-physics field characteristics of proposed MR gel clutch with five kinds of MR gels are studied and compared in order to give some useful suggestions in the design phase. Finally, the dynamic torque of the MR clutch with different MR gel is experimentally evaluated.

Modeling local scour around complex bridge supports using CFD and a shear-stresses-based simplified approach

This study presents a simplified numerical modeling approach that estimates the local scour depths around bridge supports based on the bed shear stresses. It is developed using 3D computational fluid dynamics and coding through ANSYS workbench scripting along with C++ language. The proposed model is called SCFDS (Simplified Computational Fluid Dynamics Scour). The model’s main idea is to lower the bed bathymetry at the locations affected by flow obstruction until the shear stresses reach stable target values. The developed model is assessed by applying it to a complex pier of a real bridge over the Nile-River, and its scour data is calculated using the Hec-18 empirical equations. The outcomes of the model’s assessment show that it can depict the local scour around complex bridge supports. The developed approach is a novel and efficient tool that can help the designers in simulating local scour in the vicinity of flow obstructions. However, more verification studies are necessary to reach a generalized conclusion.

The Anti/Deicing Performance of the Low Interfacial Toughness Coating Is Enhanced: Induced Ice Crack Generation and Its Extension.

The low interfacial toughness of the material surface is important for crack initiation and expansion of the ice layer as it remains an effective method for large-scale deicing. However, there are challenges, such as a large critical icing size and incomplete shedding of the ice layer. Adjusting the interfacial forces to make the ice more prone to cracking, expanding, and shedding is advantageous in addressing the problem of anti-icing failure in materials with low interfacial toughness. Therefore, we propose a deicing strategy that combines porous PDMS (polydimethylsiloxane) coatings with low interfacial toughness and piezoelectric vibration. A series of hydrophobic porous PDMS coatings with different porosities were prepared on the surface of an aluminum alloy substrate through curing and phase separation. The elastic modulus of the coatings decreased from 1465 to 509 kPa as the coating porosity increased, revealing the mechanism behind the improvement in mechanical properties. The key to promoting ice fracture on porous PDMS coatings lies in the synergistic effect of the out-of-plane shear stress and microcracks at the solid-ice interface. This work focuses on exploring the characteristics of interfacial forces by combining the intrinsic mechanical properties of coatings with external forces, providing new insights for designing low interfacial toughness anti-icing materials.

Experimental and Numerical Indentation Tests to Study the Crack Growth Properties Caused by Various Indenters Under High Temperature

ABSTRACTThis paper investigates the influence of indenter shape and rock texture on the crack growth properties and rock hardness. For this purpose, two different rock specimens such as basalt and marble with various textures were prepared and tested by Vickers indentation hardness device with rhombus indenter shape under two different temperatures of 35°C and 100°C. Concurrent with the experimental test, Vickers indentation simulations have been done on three calibrated rock models with nine different indenter shapes. The tensile strength of marble was 8 MPa, while basalt had a tensile strength of 10.8 MPa. Regarding compressive strength, marble exhibited 71 MPa, whereas basalt had a compressive strength of 153 MPa. Marble and basalt had elastic moduli of 45 and 95 GPa, respectively. The physical loading was applied vertically at a rate of 0.004 mm/min. The rock's texture and temperature significantly impact Vickers indentation hardness. Penetration by the Vickers indenter creates an elastic‐plastic stress field, leading to radial cracks due to exceeding the critical stress level. Ring cracks are caused by bulging of the test material and nested cracks directly under the indentation due to high shear and bending stresses in the region. The indentation shape affected the extent of the damage zone below it, leading to increased crack growth with smaller indentation diameters. The radial fracture number increased when the cross‐section changed from circular to quadrilateral shape. The crack growth and damage zone area increased with higher rock temperature due to increased rock brittleness.

Experimental and Numerical Study on Nonlinear Shear Behavior and Constitutive Model of Deep Shale Laminae Planes

The direct shear tests showed that the degradation of unevenness and waviness of the laminae plane is the primary reason for the dynamic decrease in shear strength. A shear constitutive model was proposed which considers the scale effect and the asperity geometry of the unevenness and waviness of the laminar plane. The evolution of the shear strength and stiffness with a normal stress and scale effect during the shearing of shale laminae planes was explored. The results show that high normal stress aggravates the stiffness hardening of laminae planes and forms larger peak shear stress and peak shear displacement. At the lab scale, the increase in the unevenness wavelength has a hardening effect on the shear stiffness and strength. The small-scale unevenness contributes most to the shear strength of shale laminae planes at the lab scale. At the field scale, the increase in the waviness wavelength has a softening effect on the shear stiffness and strength.

Tribocorrosion Performance and Cytotoxicity of Additive Manufactured CoCrMo: A Benchmark Against Wrought CoCrMo

Additive Manufacturing (AM) has increasingly gained attention as a tool for the fabrication of complex biomedical components, due to the flexibility of the technique for accounting to the patient individuality. Additive manufacturing techniques, like laser beam melting, often result in highly anisotropic microstructures that greatly differ from those obtained in conventionally manufactured alloys. This study evaluates the potential of AM manufactured CoCrMo for body implants as an alternative to the wrought CoCrMo, especially considering tribocorrosion performance in buffered fluid. Its biocompatibility is also assessed via in-vitro cytotoxicity assays. The results show that both materials have a comparable tribocorrosion performance, independently of the manufacturing process, despite their radically different initial microstructure. This results from the microstructural convergence arising from the plastic deformation imparted by sliding motion. While the initially elongated grains of the AM CoCrMo tend to grain refinement, the microstructure of the wrought CoCrMo undergoes grain coarsening, resulting in a similar final grain size detected after the tribocorrosion experiments. The addition of albumin to the phosphate buffer testing fluid, simulating body fluid applications, reduces the grain refinement, particularly under constant 0.21 V, due to lower shear stresses caused by the lower coefficient of friction. Therefore, the initial dissimilarity found in the untested microstructure between the materials does not affect the wear rate nor lead to an increased metal release. As the cytotoxicity is neither impaired by the manufacturing process, the use of AM CoCrMo could be recommended on those biomedical applications requiring wear resistance in body fluid environment.

Theoretical Prediction of Crystal Structure of Mo2Ga2B and Its Evolution to Layered Boride Mo2B

Conventional Mn+1AXn phases are a large family of compounds that have been limited to carbides and nitrides. Herein, the stable structure of Mo2Ga2B, a typical boron‐based ternary phase in the Mo‐Ga‐B system, using a computational structure search approach is predicted. The predicted hexagonal‐layered structure is the typical structure of traditional Mn+1AXn phases, and two Ga layers separate Mo2B blocks in Mo2Ga2B, which is different from the M2AX phases. The analysis of phonon dispersions and elastic constants confirms that the hexagonal‐layered structure exhibits both dynamical and mechanical stability, respectively. The tensile and shear stress–strain curves are obtained, and the structural stability is investigated by analyzing the stability of chemical bonds under tensile and shear deformations. Layered Mo2B can be obtained by the removal of Ga layer from the precursor Mo2Ga2B. Theoretical predictions indicate that monolayer Mo2B is metallic, and has potential applications as an anode and thermoelectric material.

3D printing molding of UV‐curing liquid silicone rubber by UV follow curing

AbstractSilicone rubber is renowned for its excellent mechanical properties and high biocompatibility. 3D printing enables the realization of more complex structures and the development of more flexible and diverse functions, providing more opportunities and a more comprehensive range of applications in aerospace, biomedical, flexible wearable, soft robotics, and other fields. However, silicone rubber is often hindered by poor rheology and low curing efficiency, which significantly affects the forming performance of the parts. Therefore, this study introduces a UV‐follow curing method for direct ink writing (UFC‐DIW) utilizing UV‐curable silicone rubber. First, a kind of liquid silicone rubber (UV‐LSR) capable of rapid curing under UV light was synthesized, both its curing kinetics and rheological behavior were thoroughly investigated. Then, UV‐LSR inks with lower shear stress were printed using the UFC‐DIW method. A comparative analysis was conducted between the overall structure produced via UFC‐DIW and parts molded through postprinting integral curing methods. The results show that while parts cured postprinting exhibit deformation correlated with printing height, those fabricated using UFC‐DIW maintain structural integrity without deformation. It demonstrates that the UFC‐DIW method can effectively improve the formability of the parts.

River suspended-sand flux computation with uncertainty estimation using water samples and high-resolution ADCP measurements

Abstract. Measuring suspended-sand fluxes in rivers remains a scientific challenge due to their high spatial and temporal variability. To capture the vertical and lateral gradients of concentration in the cross-section, measurements with point samples are performed. However, the uncertainty related to these measurements is rarely evaluated, as few studies of the major sources of error exist. Therefore, the aim of this study is to develop a method to determine the cross-sectional sand flux and estimate its uncertainty. This SDC (for sand discharge computing) method combines suspended-sand concentrations from point samples with ADCP (acoustic Doppler current profiler) high-resolution depth and velocity measurements. The MAP (for multitransect averaged profile) method allows obtaining an average of several ADCP transects on a regular grid, including the unmeasured areas. The suspended-sand concentrations are integrated vertically by fitting a theoretical exponential suspended-sand profile to the data using Bayesian modeling. The lateral integration is based on the water depth as a proxy for the local bed shear stress to evaluate the bed concentration and sediment diffusion along the river cross-section. The estimation of uncertainty combines ISO standards and semi-empirical methods with a Bayesian approach to estimate the uncertainty due to the vertical integration. The new method is applied to data collected in four rivers under various hydro-sedimentary conditions: the Colorado, Rhône, Isère, and Amazon rivers, with computed flux uncertainties ranging between 18 % and 32 %. The relative difference between the suspended-sand flux in 21 cases calculated with the proposed SDC method compared to the International Organization for Standardization (ISO) 4363 standard method ranges between −40 % and +23 %. This method that comes with a flexible, open-source code is the first to propose an applicable uncertainty estimation that could be adapted to other flux computation methods.

Influence of speed and line spacing on aerodynamic forces in high speed train passing in tunnels

As train speeds increase, the aerodynamic effects generated during the passage of high-speed trains in tunnels become more pronounced. This article investigates the influence of line spacing on the aerodynamic forces during the passage of high-speed trains in tunnels at different speeds. The research methodology is based on the three-dimensional transient compressible Reynolds-averaged Navier-Stokes (RANS) equations and the k-ω Shear Stress Transport (SST) turbulence model, using overset grid technology to simulate the train passing process in the tunnel. The results show that the aerodynamic drag, lateral force, and lift experienced by the train increase as the line spacing decreases and as the speed increases. line spacing has the greatest impact on aerodynamic lift, followed by lateral force, with drag having the smallest impact. Compared to line spacing, speed has a much larger effect on aerodynamic forces. The aerodynamic forces experienced by the train during tunnel passage are proportional to the square of the train’s speed and have an exponential relationship with the line spacing during train passage.

A High-Fidelity Computational Model for Predicting Blood Cell Trafficking and 3D Capillary Hemodynamics in Retinal Microvascular Networks.

To present a first principle-based, high-fidelity computational model for predicting full three-dimensional (3D) and time-resolved retinal microvascular hemodynamics taking into consideration the flow and deformation of individual blood cells. The computational model is a 3D fluid-structure interaction model based on combined finite volume/finite element/immersed-boundary methods. Three in silico microvascular networks are built from high-resolution in vivo motion contrast images of the superficial capillary plexus in the parafoveal region of the human retina. The maximum tissue area represented in the model is approximately 500 × 500 µm2, and vessel lumen diameters ranged from 5.5 to 25 µm covering capillaries, arterioles, and venules. Blood is modeled as a suspension of individual blood cells, namely, erythrocytes (RBC), leukocytes (WBC), and platelets in plasma. An accurate and detailed biophysical modeling of each blood cell and their flow-induced deformation is considered. A physiological, pulsatile boundary condition corresponding to an average cardiac cycle of 0.9 second is used. Detailed quantitative data and analysis of 3D retinal microvascular hemodynamics are presented, and their relationship to RBC flow dynamics is illustrated. Blood velocity is shown to have temporal oscillations superimposed on the background pulsatile variation, which arise because of the way RBCs partition at vascular junctions, causing repeated clogging and unclogging of vessels. Temporal variations in RBC velocity and hematocrit are anti-correlated in a given vessel, but their time-averaged distributions are positively correlated across the network. Whole blood velocity is 65% to 85% of RBC velocity, with the discrepancy related to the formation of an RBC-free region, adjacent to the vascular endothelium and typically 0.8 to 1.8 µm thick. The 3D velocity and RBC concentration profiles are shown to be oppositely skewed with respect to each other, because of the way that RBCs "hug" the apex of each bifurcation. RBC deformation is predicted to have biphasic behavior with respect to vessel diameter, with minimal cell length for vessels approximately 7 µm in diameter. The wall shear stress (WSS) exhibits a strongly 3D distribution with local regions of high value and gradient spanning a range of 10 to 80 dyn/cm2. WSS is highest where there is faster flow, greater curvature of the vessel wall, capillary bifurcations, and at locations of RBC crowding and associated thinning of the cell-free layer. This study highlights the usefulness of high-fidelity cell-resolved modeling to obtain accurate and detailed 3D, time-resolved retinal hemodynamic parameters that are not readily available through noninvasive imaging approaches. The results presented are expected to complement and enhance the interpretation of in vivo data, as well as open new avenues to study retinal hemodynamics in health and disease.

Kindlin-2 Phase Separation in Response to Flow Controls Vascular Stability.

Atheroprotective shear stress preserves endothelial barrier function, while atheroprone shear stress enhances endothelial permeability. Yet, the underlying mechanisms through which distinct flow patterns regulate EC integrity remain to be clarified. This study aimed to investigate the involvement of Kindlin-2, a key component of focal adhesion and endothelial adherens junctions crucial for regulating endothelial cell (EC) integrity and vascular stability. Mouse models of atherosclerosis in EC-specific Kindlin-2 knockout mice (Kindlin-2iΔEC) were used to study the role of Kindlin-2 in atherogenesis. Pulsatile shear (2±4 dynes/cm2) or oscillatory shear (0.5±4 dynes/cm2) were applied to culture ECs. Live-cell imaging, fluorescence recovery after photobleaching assay, and optoDroplet assay were used to study the liquid-liquid phase separation (LLPS) of Kindlin-2. Co-immunoprecipitation, mutagenesis, proximity ligation assay, and transendothelial electrical resistance assay were used to explore the underlying mechanism of flow-regulated Kindlin-2 function. We found that Kindlin-2 localization is altered under different flow patterns. Kindlin-2iΔEC mice showed heightened vascular permeability. Kindlin-2iΔEC were bred onto ApoE-/- mice to generate Kindlin-2iΔEC; ApoE-/- mice, which displayed a significant increase in atherosclerosis lesions. In vitro data showed that in ECs, Kindlin-2 underwent LLPS, a critical process for proper focal adhesion assembly, maturation, and junction formation. Mass spectrometry analysis revealed that oscillatory shear increased arginine methylation of Kindlin-2, catalyzed by PRMT5 (protein arginine methyltransferase 5). Functionally, arginine hypermethylation inhibits Kindlin-2 LLPS, impairing focal adhesion assembly and junction maturation. Notably, we identified R290 of Kindlin-2 as a crucial residue for LLPS and a key site for arginine methylation. Finally, pharmacologically inhibiting arginine methylation reduces EC activation and plaque formation. Collectively, our study elucidates that mechanical force induces arginine methylation of Kindlin-2, thereby regulating vascular stability through its impact on Kindlin-2 LLPS. Targeting Kindlin-2 arginine methylation emerges as a promising hemodynamic-based strategy for treating vascular disorders and atherosclerosis. URL: https://www.clinicaltrials.gov; Unique identifier: NCT02783300.

Branching and nonbranching intracranial aneurysms in the presence of a persistent stapedial artery and an aberrant internal carotid artery assessed with computational hemodynamics: illustrative case.

The mechanisms underlying the initiation and progression of bifurcation versus lateral wall aneurysms are not well understood. Computational fluid dynamics (CFD) can improve the understanding of these mechanisms and can consequently help identify patients at higher risk for developing aneurysms and monitor them more closely. A 36-year-old man presented with a ruptured anterior communicating artery aneurysm, which was successfully treated with microsurgical clipping. Imaging also revealed a persistent stapedial artery with an elongated and tortuous posterior communicating artery (PComA). Fourteen years later, he was readmitted for a ruptured aneurysm on a PComA loop. CFD helped identify considerable collateral circulation due to the aberrant internal carotid artery (ICA). High flow rates trigger both types of aneurysms, but nuances exist in the hemodynamic mechanisms that drive their growth. Berry aneurysms and lateral wall aneurysms initially start due to a high flow rate, a common underlying cause. However, the formation of true sidewall aneurysms is primarily characterized by locally increased wall shear stress, while the development of berry aneurysms is mainly linked to high local blood pressure at arterial bifurcations. An aberrant ICA can lead to supraphysiological compensatory flow in the anterior and posterior circulation, increasing the risk of intracranial aneurysm formation at both branching and nonbranching sites, underscoring the need for lifelong monitoring. https://thejns.org/doi/10.3171/CASE24421.

The Correlation of Vessel Wall Macrophage Infiltration with Hemosiderin in Arteriovenous Malformations

Endothelial dysfunction, induced by high shear stress from increased nidal blood flow, may promote a cycle of inflammation, possibly leading to instability and cerebral arteriovenous malformations (AVMs) rupture. Macrophages, identified with CD68, are key inflammatory components in AVM pathology. We aim to evaluate the relationship of inflammation with AVM flow and hemosiderin. This is a retrospective study of archived tissue. Adult patients (2002-2022) with baseline quantitative magnetic resonance angiography (QMRA) imaging, no embolization, and history of microsurgical resection (n=17), with both ruptured (n=9) and unruptured cases (n=8). Brain AVM sections were stained with CD68 to quantify vessel wall macrophage infiltration and hematoxylin and eosin stain as a control and to quantify hemosiderin. QMRA with noninvasive optimal vessel analysis (NOVA) was reviewed, and AVM flow was calculated. Statistical analyses were performed. There were no significant differences between macrophage infiltration and patient demographics, Spetzler-Martin grade, eloquence, venous stenosis, nidus compactness, volume, and AVM flow. Vessel wall macrophage infiltration positively correlated with patients who presented with confirmed AVM rupture (163.8 +/- 46.7 vs. 101.3 +/- 49.4, p=0.017). Increases in vessel wall macrophage infiltration were found to positively correlate with higher grades of hemosiderin (p=0.023), except for grade 4 hemosiderin. Venous anomaly showed a negative association with macrophage infiltration (p=0.035). These findings suggest a relationship between AVM vessel wall inflammation, hemosiderin, and hemorrhage presentation. Further investigations with larger sample sizes are warranted to understand the role of altered hemodynamics, hemosiderin deposition and inflammation in AVM vessel walls.

Low, but Not High, Pulsating Fluid Shear Stress Affects Matrix Extracellular Phosphoglycoprotein Expression, Mainly via Integrin β Subunits in Pre-Osteoblasts

Matrix extracellular phosphoglycoprotein (Mepe), present in bone and dentin, plays important multifunctional roles in cell signaling, bone mineralization, and phosphate homeostasis. Mepe expression in bone cells changes in response to pulsating fluid shear stress (PFSS), which is transmitted into cells through integrin-based adhesion sites, i.e., α and β subunits. Whether and to what extent PFSS influences Mepe expression through the modulation of integrin α and/or β subunit expression in pre-osteoblasts is uncertain. Therefore, we aimed to test whether low and/or high PFSS affects Mepe expression via modulation of integrin α and/or β subunit expression. MC3T3-E1 pre-osteoblasts were treated with ± 1 h PFSS (magnitude: 0.3 Pa (low PFSS) or 0.7 Pa (high PFSS); frequency: 1 Hz). Single integrin fluorescence intensity in pre-osteoblasts was increased, but single integrin area was decreased by low and high PFSS. Expression of two integrin α subunit-related genes (Itga1 and Itga5 2) was increased by low PFSS, and one (Itga5 2) by high PFSS. Expression of five integrin β subunit genes (Itgb1, Itgb3, Itgb5, Itgb5 13, and Itgb5 123) was increased by low PFSS, and three (Itgb5, Itgb5 13, and Itgb5 123) by high PFSS. Interestingly, Mepe expression in pre-osteoblasts was only modulated by low, but not high, PFSS. In conclusion, both low and high PFSS affected integrin α and β subunit expression in pre-osteoblasts, while integrin β subunit expression was more altered by low PFSS. Importantly, Mepe gene expression was only affected by low PFSS. These results might explain the different ways that Mepe-induced changes in pre-osteoblast mechanosensitivity may drive signaling pathways of bone cell function at low or high impact loading. These findings might have physiological and biomedical implications and require future research specifically addressing the precise role of integrin α or β subunits and Mepe during dynamic loading in bone health and disease.

Effective Concrete Failure Area for SC Structures Using Stud and Tie Bar Under Performance Tests.

Nuclear power plants, where steel-plate concrete (SC) structures are commonly adopted, require large-scale components to withstand significant loads, such as those caused by sudden explosions. As a result, SC modular members used in nuclear power plants must have thicker walls filled with concrete compared to standard-sized ones. These large walls also require additional components, such as tie bars and H-shaped steel sections, to reinforce adhesion and resist shear stresses. This study focuses on tie bars placed adjacent to studs and evaluates their influence on the tensile strength of wall structures. To investigate this, we conducted experimental tests using full-scale specimens, including various combinations ranging from single stud to combined stud-tie configurations. Based on the results of these performance tests, we propose a design recommendation for estimating the tensile capacity of SC structures, considering the influence of tie bars.