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How do vessels find optimal radii? Capillaries are known to adapt their radii to maintain the shear stress of blood flow at the vessel wall at a set point, yet models of adaptation purely based on average shear stress have not been able to produce complex loopy networks that resemble real microvascular systems. For narrow vessels where red blood cells travel in a single file, the shear stress on vessel endothelium peaks sharply when a red blood cell passes through. We show that stable shear-stress-based adaptation is possible if vessel shear stress set points are cued to the stress peaks. Model networks that respond to peak stresses alone can quantitatively reproduce the observed zebrafish trunk microcirculation, including its adaptive trajectory when hematocrit changes or parts of the network are amputated. Our work reveals the potential for mechanotransduction alone to generate stable hydraulically tuned microvascular networks.

BACKGROUND: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), responsible for COVID-19, has caused nearly 7 million deaths worldwide. Severe cases are marked by an aggressive inflammatory response known as hypercytokinemia, contributing to endothelial damage. Although vaccination has reduced hospitalizations, hypercytokinemia persists in breakthrough infections, emphasizing the need for disease models mimicking this response. Using a 3D microphysiological system (MPS), we explored the vascular role in SARS-CoV-2-induced hypercytokinemia. METHODS: The vascularized micro-organ (VMO) MPS, consisting of human-derived primary endothelial cells (ECs) and stromal cells within an extracellular matrix, was used to model SARS-CoV-2 infection. A non-replicative pseudotyped virus fused to GFP was employed, allowing visualization of viral entry into human ECs under physiologic flow conditions. Expression of ACE2, TMPRSS2, and AGTR1 was analyzed, and the impact of viral infection on ACE2 expression, vascular inflammation, and vascular morphology was assessed. RESULTS: The VMO platform facilitated the study of COVID-19 vasculature infection, revealing that ACE2 expression increased significantly in direct response to shear stress, thereby enhancing susceptibility to infection by pseudotyped SARS-CoV-2. Infected ECs secreted pro-inflammatory cytokines, including IL-6 along with coagulation factors. Cytokines released by infected cells were able to activate downstream, non-infected EC, providing an amplification mechanism for inflammation and coagulopathy. DISCUSSION: Our findings highlight the crucial role of vasculature in COVID-19 pathogenesis, emphasizing the significance of flow-induced ACE2 expression and subsequent inflammatory responses. The VMO provides a valuable tool for studying SARS-CoV-2 infection dynamics and evaluating potential therapeutics.

Endothelial cells of mammalian blood vessels have multiple levels of heterogeneity along the vascular tree and among different organs. Further heterogeneity results from blood flow turbulence and variations in shear stress. In the aorta, vascular endothelial protein tyrosine phosphatase (VE-PTP), which dephosphorylates tyrosine kinase receptor Tie2 in the plasma membrane, undergoes downstream polarization and endocytosis in endothelial cells exposed to laminar flow and high shear stress. VE-PTP sequestration promotes Tie2 phosphorylation at tyrosine992 and endothelial barrier tightening. The present study characterized the heterogeneity of VE-PTP polarization, Tie2-pY992 and total Tie2, and claudin-5 in anatomically defined regions of endothelial cells in the mouse descending thoracic aorta, where laminar flow is variable and IgG extravasation is patchy. We discovered that VE-PTP and Tie2-pY992 had mosaic patterns, unlike the uniform distribution of total Tie2. Claudin-5 at tight junctions also had a mosaic pattern, whereas VE-cadherin at adherens junctions bordered all endothelial cells. Importantly, the amounts of Tie2-pY992 and claudin-5 in aortic endothelial cells correlated with downstream polarization of VE-PTP. VE-PTP and Tie2-pY992 also had mosaic patterns in the vena cava, but claudin-5 was nearly absent and extravasated IgG was ubiquitous. Correlation of Tie2-pY992 and claudin-5 with VE-PTP polarization supports their collective interaction in the regulation of endothelial barrier function in the aorta, yet differences between the aorta and vena cava indicate additional flow-related determinants of permeability. Together, the results highlight new levels of endothelial cell functional mosaicism in the aorta and vena cava, where blood flow dynamics are well known to be heterogeneous.

AbstractThe application of balloon dilation catheters in the management of intracranial arterial stenosis has been gradually increasing. However, studies on the feasibility and effectiveness of different types of balloons remain relatively scarce. In this study, catheter models of three different materials were designed to simulate balloon crimping,splitting, and dilatation processes. A compliant balloon produces large deformations with poor dilatation and a stress concentration phenomenon. During dilatation, the shear stress generated in the intima and lesion area by the semi-compliant balloon was smaller than that generated by the non-compliant balloon. These results demonstrate the feasibility of using semi-compatible balloons. [ABSTRACT FROM AUTHOR]

Introduction: Elevated luminal homocysteine has been linked with cardiovascular disease; however, whether there is a direct effect of homocysteine on blood vessel endothelium is not clear. In this study, the acute effect of luminal homocysteine on iliac artery endothelial function was assessed in the anaesthetised pig. Methods: Hyperhomocysteinaemic blood was injected into an occluded segment of the iliac in the anaesthetised pig for 20 min, and the effect on atrial diameter during the occlusion and during the reactive hyperaemia assessed. Results: No significant changes in arterial diameter or pressure were observed during the incubation period at homocysteine concentrations of 10, 20, 40 and 100 µM. There was also no difference in the magnitude of the iliac diameter increase in the response to reactive hyperaemia when the incubation period was completed. Conclusion: There is no evidence of endothelial dysfunction in response to an acute 20-min elevation in homocysteine in an intact conduit artery. [ABSTRACT FROM AUTHOR]

This research examined the impact of aerobic exercise intensity and dose on acute post‐exercise cerebral shear stress and blood flow. Fourteen young adults (27 ± 5 years of age, eight females) completed a maximal oxygen uptake (V̇O2max${{\dot{V}}_{{{{\mathrm{O}}}_2}\max }}$) treadmill test followed by three randomized study visits: treadmill exercise at 30% of V̇O2max${{\dot{V}}_{{{{\mathrm{O}}}_2}\max }}$ for 30 min, 70% of V̇O2max${{\dot{V}}_{{{{\mathrm{O}}}_2}\max }}$ for 30 min and 70% of V̇O2max${{\dot{V}}_{{{{\mathrm{O}}}_2}\max }}$ for a duration that resulted in caloric expenditure equal to that in the 30% V̇O2max${{\dot{V}}_{{{{\mathrm{O}}}_2}\max }}$ visit (EqEE). A venous blood draw and internal carotid artery (ICA) ultrasound were collected before and immediately following exercise. ICA diameter and blood velocity were determined using automated edge detection software, and blood flow was calculated. Using measures of blood viscosity, shear stress was calculated. Aerobic exercise increased ICA shear stress (time: P = 0.005, condition: P = 0.012) and the increase was greater following exercise at 70% V̇O2max${{\dot{V}}_{{{{\mathrm{O}}}_2}\max }}$ (∆4.1 ± 3.5 dyn/cm2) compared with 30% V̇O2max${{\dot{V}}_{{{{\mathrm{O}}}_2}\max }}$ (∆1.1 ± 1.9 dyn/cm2; P = 0.041). ICA blood flow remained elevated following exercise (time: P = 0.002, condition: P = 0.010) with greater increases after 70% V̇O2max${{\dot{V}}_{{{{\mathrm{O}}}_2}\max }}$ (Δ268 ± 150 mL/min) compared with 30% V̇O2max${{\dot{V}}_{{{{\mathrm{O}}}_2}\max }}$ (∆125 ± 149 mL/min; P = 0.041) or 70% V̇O2max${{\dot{V}}_{{{{\mathrm{O}}}_2}\max }}$ EqEE (∆127 ± 177 mL/min; P = 0.004). Therefore, aerobic exercise resulted in both intensity‐ and dose‐dependent effects on acute post‐exercise ICA blood flow whereby vigorous intensity exercise provoked a larger increase in ICA blood flow compared to light intensity exercise when performed at a higher dose. What is the central question of this study?What are the independent and combined effects of exercise intensity and dose on post‐exercise internal carotid artery (ICA) haemodynamics?What is the main finding and its importance?The combined effects of exercise intensity and dose evoked the greatest haemodynamic response whereby vigorous intensity exercise for a longer duration resulted in the greatest increase in post‐exercise ICA blood flow. Therefore, exercise intensity and dose are important considerations for utilizing exercise to improve cerebrovascular function. [ABSTRACT FROM AUTHOR]

Background: The ductus arteriosus (DA) is critical in maintaining postnatal circulation in neonates with obstructed systemic circulation (OSC) and pulmonary circulation (OPC). We hypothesized that the size of the DA and aortic isthmus (AoI) undergoes adaptive growth in utero to counteract the hemodynamic challenges in these congenital heart diseases (CHD). Methods: Postnatal echocardiograms of neonates diagnosed prenatally with ductal-dependent CHD who were started on prostaglandins within 24 h of birth were reviewed. We assessed the cross-sectional area of the aortic valve opening, pulmonary valve opening, AoI, and DA by calculating (diameter)2/body surface area. Neonates were classified into OSC or OPC then subgrouped depending upon the patency of semilunar valves: OSC with and without aortic atresia (OSC-AA and OSC-nAA, respectively) and OPC with and without pulmonary atresia (OPC-PA and OPC-nPA, respectively). Results: Ninety-four cases were studied. The DA in OSC was significantly larger than OPC, and the DA in OSC-AA was significantly larger than OSC-nAA. The size of the AoI was significantly larger in OPC than OSC and larger in OSC-AA than OSC-nAA. Within the OSC-nAA group, there was no significant difference in the size of the DA, AoI, or pulmonary valve opening between those with retrograde flow (RF) at the AoI and without (nRF) except the aortic valve opening was significantly larger in nRF. All groups had comparable cross-sectional areas of systemic output. Conclusions: Our findings suggest that DA and AoI show compensatory growth to maintain critical blood flow to vital organs against primary anatomical abnormalities in ductus-dependent CHD. (249 words) [ABSTRACT FROM AUTHOR]

As the innermost monolayer of the vasculature, endothelial cells (ECs) serve as the interface for multiplex signal transduction. Directly exposed to blood-borne factors, both endogenous and exogenous, ECs actively mediate vascular homeostasis and represent a therapeutic target against cardiometabolic diseases. ECs act as the first-line gateway between gut-derived substances and vasculature. Additionally, ECs convert blood flow-exerted hemodynamic forces into downstream biochemical signaling to modulate vascular pathophysiology. Besides, ECs can sense other forms of stimuli, like cell extrusion, thermal stimulation, photostimulation, radiation, magnetic field, noise, and gravity. Future efforts are still needed to deepen our understanding on endothelial biology. [Display omitted] • ECs are interfaces for multiplex signal transduction in the vasculature. • ECs are gatekeepers between gut-derived substances and vasculature. • ECs convert hemodynamic forces to biochemical signals, mediating vasopathology. • ECs are sensitive to various environmental stimuli. [ABSTRACT FROM AUTHOR]

Skeletal muscle trauma such as fracture or crush injury can result in a life‐threatening condition called acute compartment syndrome (ACS), which involves elevated compartmental pressure within a closed osteo‐fascial compartment, leading to collapse of the microvasculature and resulting in necrosis of the tissue due to ischemia. Diagnosis of ACS is complex and controversial due to the lack of standardized objective methods, which results in high rates of misdiagnosis/late diagnosis, leading to permanent neuro‐muscular damage. ACS pathophysiology is poorly understood at a cellular level due to the lack of physiologically relevant models. In this context, microfluidics organ‐on‐chip systems (OOCs) provide an exciting opportunity to investigate the cellular mechanisms of microvascular dysfunction that leads to ACS. In this article, the state‐of‐the‐art OOCs designs and strategies used to investigate microvasculature dysfunction mechanisms is reviewed. The differential effects of hemodynamic shear stress on endothelial cell characteristics such as morphology, permeability, and inflammation, all of which are altered during microvascular dysfunction is highlighted. The article then critically reviews the importance of microfluidics to investigate closely related microvascular pathologies that cause ACS. The article concludes by discussing potential biomarkers of ACS with a special emphasis on glycocalyx and providing a future perspective. [ABSTRACT FROM AUTHOR]

Cold‐induced vasoconstriction is a significant contributor that leads to chilblains and hypothermia in humans. However, current animal models have limitations in replicating cold‐induced acral injury due to their low sensitivity to cold. Moreover, existing in vitro vascular chips composed of endothelial cells and perfusion systems lack temperature responsiveness, failing to simulate the vasoconstriction observed under cold stress. This study presents a novel approach where a microfluidic bioreactor of vessel‐on‐a‐chip was developed by grafting the inner microchannel surface of polydimethylsiloxane with a thermosensitive hydrogel skin composed of N‐isopropyl acrylamide and gelatin methacrylamide. With a lower critical solution temperature set at 30°C, the gel layer exhibited swelling at low temperatures, reducing the flow rate inside the channel by 10% when the temperature dropped from 37°C to 4°C. This well mimicked the blood stasis observed in capillary vessels in vivo. The vessel‐on‐a‐chip was further constructed by culturing endothelial cells on the surface of the thermosensitive hydrogel layer, and a perfused medium was introduced to the cells to provide a physiological shear stress. Notably, cold stimulation of the vessel‐on‐a‐chip led to cell necrosis, mitochondrial membrane potential (ΔΨm) collapse, cytoskeleton disaggregation, and increased levels of reactive oxygen species. In contrast, the static culture of endothelial cells showed limited response to cold exposure. By faithfully replicating cold‐induced endothelial injury, this groundbreaking thermosensitive vessel‐on‐a‐chip technology offers promising advancements in the study of cold‐induced cardiovascular diseases, including pathogenesis and therapeutic drug screening. [ABSTRACT FROM AUTHOR]

Endothelial shear stress is a tangential stress derived from the friction of the flowing blood on the endothelial surface of the arterial wall and is expressed in units of force/unit area (dyne/cm2). Branches and bends of arteries are exposed to complex blood flow patterns that generate low or oscillatory endothelial shear stress, which impairs glycocalyx integrity, cytoskeleton arrangement and endothelial junctions (adherens junctions, tight junctions, gap junctions), thus increasing endothelial permeability. The lipoproteins and inflammatory cells penetrating intima due to the increased endothelial permeability characterizes the pathological changes in early stage of atherosclerosis. Endothelial cells are critical sensors of shear stress, however, the mechanisms by which the complex shear stress regulate endothelial permeability in atherosclerosis remain unclear. In this review, we focus on the molecular mechanisms of the endothelial permeability induced by low or oscillatory shear stress, which will shed a novel sight in early stage of atherosclerosis. [ABSTRACT FROM AUTHOR]

The development of supportable, cost-effective, and high-performance nanoparticles (NPs) is one of the new examination points within penetrating applications. The consideration of tailorable nanoparticles offers the chance to figure out water-based drilling fluids (WBDFs) with upgraded properties, providing exceptional opportunities in the energy, oil, gas, water, or framework enterprises. In WBDFs, nano and micron materials are investigated to control their rheological properties and their influence. This paper aims to analyze the influence of nano Fe2O3 on the rheological behavior of drilling fluid muds under high temperatures and pressure. Additionally, we seek to identify the optimal concentration of iron oxide nanoparticles that maintain consistent rheology; we examined the interfering effects of shear rates and iron oxide nanoparticle temperature on the sheartype of the changed depleting liquid in the Dibella oil field to make the penetrating activity efficient, realistic, and skilled. We observe that as the temperature increases, the water-based mud (WBM), plastic viscosity (PV), yield point (YP), and gel strength (Gs) decrease until the reject structure is disrupted. Therefore, we must proceed with our assessment using nano Fe2O3 to resolve the shortcomings of the slope framework. Six water-based mud cakes containing 0.5, 1, 1.5, 2, 2.5, and 3g weight percent of iron oxide (Fe2O3) nanoparticles were prepared for this evaluation. The experimental outcomes revealed an optimal nanoparticle mixing of 2.5 g weight percent, which resulted in a 13.8% reduction in the API filtrate volume and a 40% reduction in filter cake thickness. At 300°F temperature and type 10.00 pressure, the results of our experiments consistently demonstrate a decrease of 14.77% in the rheological properties of PV and YP and 10 s and 10 min in the gel strength of carbon oxide nanoparticles. The YP-PV span is 2.7, and the yield strength is 11 lb/100 ft2. On the other hand, mud cake A, which contains 0.5 wt% NPs, loses 6 mL of fluid after 30 min. In contrast, drilling mud cake E, which is composed of 3 wt% NPs, shows a fluid loss of 5.1 mL in the API filter press test. Based on the Bingham plastic model, the maximum shear stress versus shear rate was observed for bentonite drilling muds E and F, with 2.5 wt% and 3 wt% NPs, respectively, and this result indicates that the use of nano Fe2O3 can effectively adjust the properties of drilling fluids. [ABSTRACT FROM AUTHOR]

Researchers have hypothesized that high-intensity interval exercise (HIIE) and moderate-intensity continuous exercise (MOD) lead to different patterns of shear stress in the brachial artery. These differing patterns of shear stress are thought to partially explain the differing chronic adaptations to these two types of exercise. No study has directly compared blood flow characteristics during HIIE and MOD. Sixteen healthy males (Age: 23 ± 3 years) completed two randomly assigned exercise visits: HIIE (10 × 1 min intervals at 90–95% of HRmax with 1 min of recovery between) or MOD (30 min at 70% of HRmax) on an electronically braked cycle ergometer. Brachial artery blood flow velocity and diameter were measured for a total of 12 min during each of the exercise sessions. Both anterograde blood flow (MOD: 191.3 ± 80.3 mL/min, HIIE: 153.9 ± 67.5 mL/min, p = 0.03) and shear rate (MOD: 203.5 ± 78.1 s−1, HIIE: 170.8 ± 55.5 s−1, p = 0.04) were higher during MOD compared to HIIE. Both retrograde blood flow (MOD: −48.7 ± 21.3 mL/min, HIIE: −63.9 ± 23.3 cm/s, p < 0.01) and shear rate (MOD: −51.5 ± 19.8 s−1, HIIE: −73.8 ± 28.4 s−1, p < 0.01) were of greater magnitude during HIIE compared to MOD. During exercise, brachial artery diameter (p = 0.34) did not differ between HIIE and MOD. Continuous moderate cycling exercise leads to higher brachial artery anterograde shear rate and blood flow, but lower retrograde shear rate and blood flow when compared to high-intensity interval exercise. These differences during exercise in blood flow characteristics could shed light on the differing chronic adaptations to these two types of exercise. [ABSTRACT FROM AUTHOR]

Background: Consumption coagulopathy and hemorrhagic syndrome are the typical features of Bothrops sp. snake envenoming. In contrast, B. lanceolatus envenoming can induce thrombotic complications. Our aim was to test whether crude B. lanceolatus and B. atrox venoms would display procoagulant activity and induce thrombus formation under flow conditions. Methods and Principal Findings: Fibrin formation in human plasma was observed for B. lanceolatus venom at 250–1000 ng/mL concentrations, which also induced clot formation in purified human fibrinogen, indicating thrombin-like activity. The degradation of fibrinogen confirmed the fibrinogenolytic activity of B. lanceolatus venom. B. lanceolatus venom displayed consistent thrombin-like and kallikrein-like activity increases in plasma conditions. The well-known procoagulant B. atrox venom activated plasmatic coagulation factors in vitro and induced firm thrombus formation under high shear rate conditions. In contrast, B. lanceolatus venom induced the formation of fragile thrombi that could not resist shear stress. Conclusions: Our results suggest that crude B. lanceolatus venom displays amidolytic activity and can activate the coagulation cascade, leading to prothrombin activation. B. lanceolatus venom induces the formation of an unstable thrombus under flow conditions, which can be prevented by the specific monovalent antivenom Bothrofav®. [ABSTRACT FROM AUTHOR]

Fluid shear stress (FSS) from blood flow, sensed by the vascular endothelial cells (ECs) that line all blood vessels, regulates vascular development during embryogenesis, controls adult vascular physiology and determines the location of atherosclerotic plaque formation. Although a number of papers have reported a crucial role for cell-cell adhesions or adhesion receptors in these processes, a recent publication has challenged this paradigm, presenting evidence that ECs can very rapidly align in fluid flow as single cells without cell–cell contacts. To address this controversy, four independent laboratories assessed EC alignment in fluid flow across a range of EC cell types. These studies demonstrate a strict requirement for cell-cell contact in shear stress sensing over timescales consistent with previous literature and inconsistent with the newly published data. [ABSTRACT FROM AUTHOR]

Background: High mechanical shear stress (HMSS) generated by blood pumps during mechanical circulatory support induces blood damage (or function alteration) not only of blood cell components but also of plasma proteins. Methods: In the present study, fresh, healthy human blood was used to prime a blood circuit assisted by a CentriMag centrifugal pump at a flow rate of 4.5 L/min under three pump pressure heads (75, 150, and 350 mm Hg) for 4 h. Blood samples were collected for analyses of plasma‐free hemoglobin (PFH), von Willebrand factor (VWF) degradation and platelet glycoprotein (GP) IIb/IIIa receptor shedding. Results: The extent of all investigated aspects of blood damage increased with increasing cross‐pump pressure and duration. Loss of high‐molecular‐weight multimers (HMWM)‐VWF in Loop 2 and Loop 3 significantly increased after 2 h. PFH, loss of HMWM‐VWF, and platelet GPIIb/IIIa receptor shedding showed a good linear correlation with mean shear stress corresponding to the three pump pressure heads. Conclusions: HMSS could damage red blood cells, cause pathological VWF degradation, and induce platelet activation and platelet receptor shedding. Different blood components can be damaged to different degrees by HMSS; VWF and VWF‐enhanced platelet activation may be more susceptible to HMSS. [ABSTRACT FROM AUTHOR]

This article provides a method by which the scour and self-burial of spherical bodies, short cylinders, and truncated cones that are induced by bichromatic and bidirectional waves could be derived. The empirical scour and self-burial depth formulas for spherical bodies, short cylinders, and truncated cones are used with a bed shear stress model beneath bichromatic and bidirectional waves. Examples of the results are given for unidirectional bichromatic and bidirectional monochromatic waves. The results appear to agree qualitatively with physical expectations. [ABSTRACT FROM AUTHOR]

High-temperature superconducting (HTS) rare-earth Ba2Cu3O7−x (REBCO) coated conductors (CCs) have significant potential in high-current and high-field applications. However, owing to the weak interface strength of the laminated composite REBCO CCs, the damage induced by the thermal mismatch stress under a combination of epoxy impregnation, cooling, and quenching can cause premature degradation of the critical current. In this study, a three-dimensional (3D) electromagnetic-thermal-mechanical model based on the H-formulation and cohesive zone model (CZM) is developed to study the critical current degradation characteristics in an epoxy-impregnated REBCO CC caused by the damage during a quench. The temperature variation, critical current degradation of the REBCO CC, and its degradation onset temperature calculated by the numerical model are in agreement with the experimental data taken from the literature. The delamination of the REBCO CC predicted by the numerical model is consistent with the experimental result. The numerical results also indicate that the shear stress is the main contributor to the damage propagation inside the REBCO CC. The premature degradation of the critical current during a quench is closely related to the interface shear strength inside the REBCO CC. Finally, the effects of the coefficient of thermal expansion (CTE) of the epoxy resin, thickness of the substrate, and substrate material on the critical current degradation characteristics of the epoxy-impregnated REBCO CC during a quench are also discussed. These results help us understand the relationship between the current-carrying degradation and damage in the HTS applications. [ABSTRACT FROM AUTHOR]

Bernoulli pads are traditionally used for noncontact pick-and-place operations in industry. The normal force produced by a Bernoulli pad allows it to adhere to an object or workpiece. In addition to the normal force, the pad produces shear forces, which allows it to clean a workpiece without contact. A direct relationship between the inlet fluid power and the shear losses motivates us to explore other methods of providing power to the system with the objective of increasing shear forces and thereby improving cleaning efficacy. Here, we numerically investigate a system in which additional mechanical power is added by rotating the Bernoulli pad. The rotating system provides additional fluid forces (normal and shear) for the same inlet fluid power. For a specific pad that we investigated, the maximum wall shear stress increased by ≈15% and the normal force changed from +1.4 N (repulsive) to -6.6 N (attractive) for change in the rotational speed by 60 rad/s. Also, for a given normal attractive force, a stable equilibrium configuration can exist for two mass flow rates, with the higher mass flowrate resulting in a higher stiffness of the flow field. [ABSTRACT FROM AUTHOR]

Efficient diffusion barriers are necessary to prevent the formation of copper-tin intermetallic compounds (IMCs) in advanced packaging for Sn/Cu micro-bumps. This study investigated the interfacial properties of solder and Ni, Co-9W, Co-20W, Co-20Fe-10W, and Co-36Fe-17W barriers and determined the thickness of IMCs formed between Sn and these barriers after up to 15 reflows. Among the five barriers, Co-36Fe-17W proved to be the most effective in inhibiting the reaction of liquid Sn solder. At the Sn/Co-W interface, CoSn3 IMC was formed, while at the Sn/Co-Fe-W interface, CoSn3 IMC and FeSn2 IMC were observed. The contact angles of these layers were measured and found to be 18°, 22°, 25°, 29°, and 27°, respectively. The results showed that an increase in W content in Co-W led to an increase in the contact angle, while the intrinsic wettability of Co-Fe-W decreased with an increase in Fe content. The shear strengths of the five joints were 27 MPa, 31 MPa, 25 MPa, 25 MPa, and 26 MPa, respectively, with different fracture modes observed. The Co-Fe-W-Sn layer was partially peeling from the diffusion barriers in SAC305/Co-20Fe-10W, and the fracture surfaces exhibited an irregular and rough state, which was attributed to the increasing Fe and W contents. These findings offer valuable insights for enhancing the reliability of electronic packages. [ABSTRACT FROM AUTHOR]

The interface shear behaviors between sand soil and concrete were analyzed considering the soil unloading and interface roughness effects by the direct shear tests. The analysis results show that the soil unloading has a negative effect on the difference in ultimate shear stress between the adjacent roughness. Regardless of the value of consolidation normal stress, the soil unloading effect can cause the ultimate shear stress decreased and the higher value of roughness corresponding to a higher decrease rate of it. The values of roughness and soil unloading degrees also have a negative effect on the residual ratio of interface shear strength fr. The influence of roughness on the interface shear dilation can be suppressed with the increased of the applied normal stress and make the interface transform gradually into the shear shrinkage state. A new test evaluation method of the interface shear influence range is proposed and compared with the theoretical analysis results. The analysis results may provide a new research approach for revealing the shear mechanism of the sand-concrete interface. [ABSTRACT FROM AUTHOR]

Stem cells are widely used in scientific research because of their ability to self-renew and differentiate into a variety of specialized cell types needed for body functions. However, the self-renewal and differentiation of stem cells are regulated by various stimuli, with mechanical stimulation being particularly notable due to its ability to mimic the physical environment in the body. This study systematically collected 2638 research papers published between 1994 and 2024, employing tools such as VOSviewer, CiteSpace, and GraphPad Prism to uncover research hotspots, publication trends, and collaboration networks. The results indicate a yearly increase in global research on the shear stress stimulation of stem cells, with significant contributions from the United States and China in terms of research investment and output. Future research directions include a deeper understanding of the mechanisms underlying mechanical stimulation's effects on stem cell differentiation, the development of new materials and scaffold designs to better replicate the natural cellular environment, and advancements in regenerative medicine. Despite considerable progress, challenges remain in translating basic research findings into clinical applications. [ABSTRACT FROM AUTHOR]

Fetal membrane (amniochorion), the innermost lining of the intrauterine cavity, surround the fetus and enclose amniotic fluid. Unlike unidirectional blood flow, amniotic fluid subtly rocks back and forth, and thus, the innermost amnion epithelial cells are continuously exposed to low levels of shear stress from fluid undulation. Here, we tested the impact of fluid motion on amnion epithelial cells (AECs) as a bearer of force impact and their potential vulnerability to cytopathologic changes that can destabilize fetal membrane functions. A previously developed amnion membrane (AM) organ-on-chip (OOC) was utilized but with dynamic flow to culture human fetal amnion membrane cells. The applied flow was modulated to perfuse culture media back and forth for 48 h to mimic fluid motion. A static culture condition was used as a negative control, and oxidative stress (OS) condition was used as a positive control representing pathophysiological changes. The impacts of fluidic motion were evaluated by measuring cell viability, cellular transition, and inflammation. Additionally, scanning electron microscopy (SEM) imaging was performed to observe microvilli formation. The results show that regardless of the applied flow rate, AECs and AMCs maintained their viability, morphology, innate meta-state, and low production of pro-inflammatory cytokines. E-cadherin expression and microvilli formation in the AECs were upregulated in a flow rate-dependent fashion; however, this did not impact cellular morphology or cellular transition or inflammation. OS treatment induced a mesenchymal morphology, significantly higher vimentin to cytokeratin 18 (CK-18) ratio, and pro-inflammatory cytokine production in AECs, whereas AMCs did not respond in any significant manner. Fluid motion and shear stress, if any, did not impact AEC cell function and did not cause inflammation. Thus, when using an amnion membrane OOC model, the inclusion of a dynamic flow environment is not necessary to mimic in utero physiologic cellular conditions of an amnion membrane. [ABSTRACT FROM AUTHOR]

During continuous-flow left ventricular assist device (CF-LVAD) support, hemodynamic shear stress causes a burden on aortic valve (AV) leaflets, leading to de novo aortic insufficiency (AI). This study investigated the influence of preoperative hemodynamic parameters on de novo AI in CF-LVAD recipients. We reviewed 125 patients who underwent CF-LVAD implantation without concomitant AV surgery between 2005 and 2018. De novo AI was defined as moderate or severe AI in those with none or trivial preoperative AI. During mean 30 ± 16 months of CF-LVAD support, de novo AI-free rate was 86% and 67% at 1 and 2 years, respectively. Multivariable analysis showed that higher right ventricular stroke work index (RVSWI) (hazard ratio, 1.12 /g/m2/beat; 95% confidence interval, 1.00–1.20; p = 0.047) and trivial grade AI (hazard ratio, 2.8; 95% confidence interval, 1.2–6.4; p = 0.020) were independent preoperative risk factors for de novo AI. The longitudinal analysis using generalized mixed effects model showed that higher RVSWI was associated with continuous AV closure after LVAD implantation (Odd ratio, 1.20/g/m2/beat; 95% confidence interval, 1.00–1.43 /g/m2/beat; p = 0.047). Right heart catheterization revealed that preoperative RVSWI was positively correlated with postoperative pump flow index in patients with continuously closed AV (r = 0.44, p = 0.04, n = 22). Preoperative higher RVSWI was a significant risk factor for de novo AI following CF-LVAD implantation. In patients with preserved right ventricular function, postoperative higher pump flow may affect AI development via hemodynamic stress on the AV. [ABSTRACT FROM AUTHOR]

Endothelial dysfunction, prevalent in cardiovascular diseases (CVDs) and linked to conditions like diabetes, hypertension, obesity, renal failure, or hypercholesterolemia, is characterized by diminished nitric oxide (NO) bioavailability—a key signaling molecule for vascular homeostasis. Current two‐dimensional (2D) in vitro studies on NO synthesis by endothelial cells (ECs) lack the crucial laminar shear stress, a vital factor in modulating the NO‐generating enzyme, endothelial nitric oxide synthase (eNOS), under physiological conditions. Here we developed a tracer‐based metabolomics approach to measure NO‐specific metabolites with mass spectrometry (MS) and show the impact of fluid flow on metabolic parameters associated with NO synthesis using 2D and 3D platforms. Specifically, we tracked the conversion of stable‐isotope labeled NO substrate L‐Arginine to L‐Citrulline and L‐Ornithine to determine eNOS activity. We demonstrated clear responses in human coronary artery endothelial cells (HCAECs) cultured with 13C6, 15N4‐L‐Arginine, and treated with eNOS stimulator, eNOS inhibitor, and arginase inhibitor. Analysis of downstream metabolites, 13C6, 15N3 L‐Citrulline and 13C5, 15N2 L‐Ornithine, revealed distinct outcomes. Additionally, we evaluated the NO metabolic status in static 2D culture and 3D microvessel models with bidirectional and unidirectional fluid flow. Our 3D model exhibited significant effects, particularly in microvessels exposed to the eNOS stimulator, as indicated by the 13C6, 15N3 L‐Citrulline/13C5, 15N2 L‐Ornithine ratio, compared to the 2D culture. The obtained results indicate that the 2D static culture mimics an endothelial dysfunction status, while the 3D model with a unidirectional fluid flow provides a more representative physiological environment that provides a better model to study endothelial dysfunction. [ABSTRACT FROM AUTHOR]

The entry and propagation of pores inside an adhesive interface between an elastomer and a rigid sphere were studied experimentally and simulated numerically. It was shown that mutually interacting events involving attachment-detachment of different segments of the elastomer to the indenter resulted in non-trivial patterns of spatially distributed contacts between them, which were additionally influenced by air penetration of the pores. [ABSTRACT FROM AUTHOR]

The luminal surface of the endothelium is exposed to dynamic blood flow patterns that are known to affect endothelial cell phenotype. While many studies have documented the phenotypic changes by gene or protein expression, less is known about the role of blood flow pattern on the endothelial cell (EC) lipidome. In this study, shotgun lipidomics was conducted on human aortic ECs (HAECs) exposed to unidirectional laminar flow (UF), disturbed flow (DF), or static conditions for 48 h. A total of 520 individual lipid species from 17 lipid subclasses were detected. Total lipid abundance was significantly increased for HAECs exposed to DF compared to UF conditions. Despite the increase in the total lipid abundance, HAECs maintained equivalent composition of each lipid subclass (% of total lipid) under DF and UF. However, by lipid composition (% of total subclass), 28 lipid species were significantly altered between DF and UF. Complimentary RNA sequencing of HAECs exposed to UF or DF revealed changes in transcripts involved in lipid metabolism. Shotgun lipidomics was also performed on HAECs exposed to proinflammatory agonists lipopolysaccharide (LPS) or Pam3CSK4 (Pam3) for 48 h. Exposure to LPS or Pam3 reshaped the EC lipidome in both unique and overlapping ways. In conclusion, exposure to flow alters the EC lipidome and ECs undergo stimulus-specific lipid reprogramming in response to proinflammatory agonist exposure. Ultimately, this work provides a resource to profile the transcriptional and lipidomic changes that occur in response to applied flow that can be accessed by the vascular biology community to further dissect and extend our understanding of endothelial lipid biology. [ABSTRACT FROM AUTHOR]

In this work, a priori analysis of machine learning (ML) strategies is carried out with the goal of data-driven wall modeling for large eddy simulation (LES) of gas turbine film cooling flows. High-fidelity flow datasets are extracted from wall-resolved LES (WRLES) of flow over a flat plate interacting with the coolant flow supplied by a single row of 7-7-7 shaped cooling holes inclined at 30 degrees with the flat plate at different blowing ratios (BR). The WRLES are performed using the high-order Nek5000 spectral element computational fluid dynamics (CFD) solver. Light gradient boosting machine (LightGBM) is employed as the ML algorithm for the data-driven wall model. Parametric tests are conducted to systematically assess the influence of a wide range of input flow features (velocity components, velocity gradients, pressure gradients, and fluid properties) on the accuracy of ML wall model with respect to prediction of wall shear stress. In addition, the use of spatial stencil and time delay is also explored within the ML wall modeling framework. It is shown that features associated with gradients of the streamwise and spanwise velocity components have a major impact on the prediction fidelity of wall model, while the effect of gradients of wall-normal velocity component is found to be negligible. Moreover, adding flow feature information from an x-y-z spatial stencil significantly improves the ML model accuracy and generalizability compared to just using local flow features from the matching location. Overall, highest prediction accuracy is achieved when both spatial stencil and time delay features are incorporated within the data-driven wall modeling paradigm. [ABSTRACT FROM AUTHOR]

Protein denaturation and aggregation resulting from the effects of interfacial stress, often enhanced by flow and shear stress, pose significant challenges in the production of therapeutic proteins and monoclonal antibodies. The influence of flow on protein stability is closely intertwined with interfacial effects. In this study, we have developed a microfluidic device capable of exposing low volume (< 320 µL) protein solutions to highly uniform shear. To disentangle the synergistic impact of flow and interfaces on protein aggregation, we fabricated two devices composed of different materials, namely poly(methyl methacrylate) (PMMA) and stainless steel. Upon application of shear, we observed formation of protein particles in the micron-size range. Notably, The number of particles generated in the steel devices was ∼ 3.5 fold lower than in the PMMA device, hinting at an interface-mediated effect. With increasing the protein concentration from 1 to 50 mg/mL we observed a saturation in the amount of aggregates, further confirming the key role of solid-liquid interfaces in inducing particle formation. Introduction of non-ionic surfactants prevented protein aggregation, even at the highest tested protein concentration and low surfactant concentrations of 0.05 mg/mL. Overall, our findings corroborate the synergistic impact of shear and interface effects on protein aggregation. The device developed in this study offers a small-scale platform for assessing the stability of antibody formulations throughout various stages of the development and manufacturing process. [ABSTRACT FROM AUTHOR]

The endothelial glycocalyx (EG), covering the luminal side of endothelial cells, regulates vascular permeability and senses wall shear stress. In sepsis, EG undergoes degradation leading to increased permeability and edema formation. We hypothesized that restoring EG integrity using liposomal nanocarriers of preassembled glycocalyx (LNPG) will restore normal venular permeability in lipopolysaccharide (LPS)-induced sepsis model of mice. To test this hypothesis, we designed a unique perfusion microchamber in which the permeability of isolated venules could be assessed by measuring the concentration of Evans blue dye (EBD) in microliter samples of extravascular solution (ES). Histamine-induced time- and dose-dependent increases in EBD in the ES could be measured, confirming the sensitivity of the microchamber system. Notably, the histamine-induced increase in permeability was significantly attenuated by histamine receptor (H1) antagonist, triprolidine hydrochloride. Subsequently, mice were treated with LPS or LPS + LNPG. When compared with control mice, venules from LPS-treated mice showed a significant increased permeability, which was significantly reduced by LNPG administration. Moreover, in the presence of wall shear stress, intraluminal administration of LNPG significantly reduced the permeability in isolated venules from LPS-treated mice. We have found no sex differences. In conclusion, our newly developed microchamber system allows us to quantitatively measure the permeability of isolated venules. LPS-induced sepsis increases permeability of mesenteric venules that is attenuated by in vivo LNPG administration, which also reestablished endothelial responses to shear stress. Thus, LNPG presents a promising therapeutic potential for restoring EG function and thereby mitigating vasogenic edema due to increased permeability in sepsis. NEW & NOTEWORTHY: In sepsis, the degradation of the endothelial glycocalyx leads to increased venular permeability. In this study, we developed a potentially new therapeutic approach by in vivo administration of liposomal nanocarriers of preassembled glycocalyx to mice, which restored venular sensitivity to wall shear stress and permeability in lipopolysaccharide-induced sepsis, likely by restoring the integrity of the endothelial glycocalyx. Using a new microchamber system, the permeability of Evans blue dye could be quantitatively determined. [ABSTRACT FROM AUTHOR]

Diabetic kidney disease (DKD) is a microvascular complication of diabetes, and glomerular endothelial cell (GEC) dysfunction is a key driver of DKD pathogenesis. Krüppel-like factor 2 (KLF2), a shear stress-induced transcription factor, is among the highly regulated genes in early DKD. In the kidney, KLF2 expression is mostly restricted to endothelial cells, but its expression is also found in immune cell subsets. KLF2 expression is upregulated in response to increased shear stress by the activation of mechanosensory receptors but suppressed by inflammatory cytokines, both of which characterize the early diabetic kidney milieu. KLF2 expression is reduced in progressive DKD and hypertensive nephropathy in humans and mice, likely due to high glucose and inflammatory cytokines such as TNF-α. However, KLF2 expression is increased in glomerular hyperfiltration-induced shear stress without metabolic dysregulation, such as in settings of unilateral nephrectomy. Lower KLF2 expression is associated with CKD progression in patients with unilateral nephrectomy, consistent with its endoprotective role. KLF2 confers endoprotection by inhibition of inflammation, thrombotic activation, and angiogenesis, and thus KLF2 is considered a protective factor for cardiovascular disease (CVD). Based on similar mechanisms, KLF2 also exhibits renoprotection, and its reduced expression in endothelial cells worsens glomerular injury and albuminuria in settings of diabetes or unilateral nephrectomy. Thus KLF2 confers endoprotective effects in both CVD and DKD, and its activators could potentially be developed as a novel class of drugs for cardiorenal protection in diabetic patients. [ABSTRACT FROM AUTHOR]

Debris floods commonly occur in steep channels with an abundant sediment supply, and they can cause significant damage, primarily due to their higher sediment concentrations and negative impacts upon bank erosion, deep scouring and aggradation. These key hazards pose challenges for traditional assessment methods, making quantification difficult. This became obvious during a recent catastrophic debris flood that occurred on July 12, 2022, in the Heishuigou catchment (102 km2), northern Sichuan Province, China. In this case study, we developed an integrated methodology for assessing this debris flood event by incorporating field surveys, hydrological and hydraulic modelling and sediment transport calculations. Detailed information such as topographic maps, photographs, deposits, grain size distributions and inundation depths was collected to analyse the material sources, validate the parameters and conduct model calculations. The peak debris flood discharge and the supra‐critical bed shear stress ratios, estimated from hydrological and dynamic models, were incorporated to analyse the debris flood's typology and characterize its destructive mechanisms. The regional frequency–volume relationship established through bedload transport calculations was calibrated using the volume of the deposits determined via field investigation. These methods not only contribute to a comprehensive understanding of debris floods but also provide valuable support for future risk assessments and mitigation designs. [ABSTRACT FROM AUTHOR]

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Abstract We propose a simple tool for liquid static culture using a copolymer film with high gas permeability. The film bags were successfully used to culture microorganisms Escherichia coli, Komagataella phaffii (methylotrophic) and Bacillus sp. (biofilm-forming), with cells cultured under physical stress-free conditions with sufficient oxygen supply. Similar growth curves and plasmid productivity were observed for liquid shake and film bag E. coli cultures. The early growth response of the film bag culture following colony inoculation of liquid media differed from conventional shake cultures. Our results indicate that a gas-permeable film bag is a promising liquid culture tool and provides novel microbiology materials.

Abstract This research examined the impact of aerobic exercise intensity and dose on acute post‐exercise cerebral shear stress and blood flow. Fourteen young adults (27 ± 5 years of age, eight females) completed a maximal oxygen uptake (V̇O2max) treadmill test followed by three randomized study visits: treadmill exercise at 30% of V̇O2max for 30 min, 70% of V̇O2max for 30 min and 70% of V̇O2max for a duration that resulted in caloric expenditure equal to that in the 30% V̇O2max visit (EqEE). A venous blood draw and internal carotid artery (ICA) ultrasound were collected before and immediately following exercise. ICA diameter and blood velocity were determined using automated edge detection software, and blood flow was calculated. Using measures of blood viscosity, shear stress was calculated. Aerobic exercise increased ICA shear stress (time: P = 0.005, condition: P = 0.012) and the increase was greater following exercise at 70% V̇O2max (∆4.1 ± 3.5 dyn/cm2) compared with 30% V̇O2max (∆1.1 ± 1.9 dyn/cm2; P = 0.041). ICA blood flow remained elevated following exercise (time: P = 0.002, condition: P = 0.010) with greater increases after 70% V̇O2max (Δ268 ± 150 mL/min) compared with 30% V̇O2max (∆125 ± 149 mL/min; P = 0.041) or 70% V̇O2max EqEE (∆127 ± 177 mL/min; P = 0.004). Therefore, aerobic exercise resulted in both intensity‐ and dose‐dependent effects on acute post‐exercise ICA blood flow whereby vigorous intensity exercise provoked a larger increase in ICA blood flow compared to light intensity exercise when performed at a higher dose.

To reveal the mechanism of shear failure of en-echelon joints under cyclic loading, such as during earthquakes, we conducted a series of cyclic shear tests of en-echelon joints under constant normal stiffness (CNS) conditions. We analyzed the evolution of shear stress, normal stress, stress path, dilatancy characteristics, and friction coefficient and revealed the failure mechanisms of en-echelon joints at different angles. The results show that the cyclic shear behavior of the en-echelon joints is closely related to the joint angle, with the shear strength at a positive angle exceeding that at a negative angle during shear cycles. As the number of cycles increases, the shear strength decreases rapidly, and the difference between the varying angles gradually decreases. Dilation occurs in the early shear cycles (1 and 2), while contraction is the main feature in later cycles (3−10). The friction coefficient decreases with the number of cycles and exhibits a more significant sensitivity to joint angles than shear cycles. The joint angle determines the asperities on the rupture surfaces and the block size, and thus determines the subsequent shear failure mode (block crushing and asperity degradation). At positive angles, block size is more greater and asperities on the rupture surface are smaller than at nonpositive angles. Therefore, the cyclic shear behavior is controlled by block crushing at positive angles and asperity degradation at negative angles.

To determine the sensitivity of vascular endothelial cells to long durations of low-intensity pulsed ultrasound (LIPUS) compared to normal flow and identify the duration that maximizes expression of two mechanosensitive genes related to healthy endothelial function, endothelial nitric oxide synthase (eNOS) and Krüppel-like factor 2 (KLF2). Custom ultrasound exposure tanks were developed and the acoustic field was characterized. Human umbilical vein endothelial cells were seeded into culture plates and exposed to LIPUS at a frequency of 1 MHz and acoustic pressure of 217 kPa for 20 min, 1 h, 6 h, 9 h, or 24 h. As a comparator, other cells were exposed to normal flow. RT-qPCR was used to assess mRNA expression of eNOS and KLF2. Maximum eNOS and KLF2 expression occurred at 6 h and was localized to the beam path. Both genes exhibited qualitatively similar patterns of expression under LIPUS compared to normal flow. LIPUS induced a more rapid beneficial response compared to normal flow, but flow induced higher expression of both genes. eNOS expression after 6 h of LIPUS was dependent on RNA yield and culture duration prior to experiments. Endothelial cells exposed to longer durations of LIPUS than typically employed exhibited greater expression of beneficial genes. The temporal gene expression patterns resulting from LIPUS and normal flow suggest activation of similar signaling pathways. However, LIPUS also caused increased RNA yield that may be linked to proliferation, which would suggest more of a wound healing than atheroprotective phenotype. [ABSTRACT FROM AUTHOR]

The application of ultrafine bubbles a.k.a. nano-bubbles (NBs) in upgrading the flotation recovery of fine particles has been extensively investigated from various perspectives over the last two decades. However, their rheological aspect has not been studied yet, which is presented for the first time in this paper. To this end, the current study addresses the effect of six crucial variables including solid content (5%, 15%, and 25% (w/w)), presence and absence of NBs, inner diameter of a Venturi tube (1.5 and 2.2 mm), pH of pulp (4.5–11) and frother dosage (3, 13, and 33 mg/L) on the variation of rheological parameters i.e. shear stress, shear tension, and viscosity. Ultrafine bubbles were generated in a conditioning tank through the hydrodynamic cavitation mechanism using a fatty-acid-based frother (Flo-Y-S), while the rheological responses were continuously monitored and measured by a rheometer and parallel plate spindle (for pulp) and a double gap spindle (for NBs). Flotation tests were conducted on a high-grade phosphate ore (d80 = 37 µm) using a mechanically agitated Denver®-type (D12) flotation cell. The experimental results revealed that fluid behavior without NBs using 13 mg/L frother was in the range of shear rates less than 1 s−1 non-Newtonian and close to the shear thinning state, while it became completely Newtonian in the range of 1 to 1500 s−1. However, the presence of NBs at the same frother content changed this tendency to non-Newtonian and Newtonian fluids at shear rates of <30 s−1 and >30 s−1, respectively. It was also found that either in acidic (5.5) or strong alkaline (11) domains, the pulp viscosity trends were almost close to each other and varied from 0.002−10 to 0.002−4 Pa.s, respectively. On the other hand, on the same trend, the amount was lowered to three times in the neutral range (7.5) and weak alkalinities (9). Diminishing the inner diameter of the Venturi tube from 2.2 mm to 1.5 mm led to an increment of shear stress and viscosity about twice at the shear rates <100 s−1. The results of evaluating frother dosage showed that an increase in the amount of frother dosage, which reduced bubble dimensions, exceeded the viscosity and the amount of shear stress. Finally, we concluded that the rheological properties significantly impacted the selective separation of NB-assisted flotation processes and need further investigations in the future. [ABSTRACT FROM AUTHOR]

Pressure ulcer (PU) is the representative skin injury and is a major limiting factor in the long-term use of the wearable robots. For the sake of the health of the wearable robot user and to improve the usability of the wearable robot, we developed a pressure ulcer breakout time estimation model (PUBTEM). The model estimates the possible breakout time of PU at the skin beneath the cuff of the wearable robot, hence, it can be used as a guide for the design, control, and operational strategy of wearable robot. To develop the model, PU breakout mechanisms were analyzed extensively in the biomechanical perspective. From the analysis, skin pressure, skin shear stress and compressive stress in muscle tissue were identified as major factors causing PU and their relationships with time were collected. However, the skin shear stress and compressive stress are either difficult or impossible to measure in the environment where the wearable robot is used. Hence, we converted those two factors into the pressure—a easily measureable quantity—by applying the FEM analysis of the human musculoskeletal model and the relationship with friction coefficient. Through this conversion process, the relationship of all three factors with PU breakout time could be modeled with respect to a single variable, the skin pressure. Finally, the most conservative relationship that has fastest PU occurrence time was established as the PUBTEM. The model was validated with the human subject experiments approved by the IRB. [ABSTRACT FROM AUTHOR]

Researchers have hypothesized that high-intensity interval exercise (HIIE) and moderate-intensity continuous exercise (MOD) lead to different patterns of shear stress in the brachial artery. These differing patterns of shear stress are thought to partially explain the differing chronic adaptations to these two types of exercise. No study has directly compared blood flow characteristics during HIIE and MOD. Sixteen healthy males (Age: 23 ± 3 years) completed two randomly assigned exercise visits: HIIE (10 × 1 min intervals at 90–95% of HRmax with 1 min of recovery between) or MOD (30 min at 70% of HRmax) on an electronically braked cycle ergometer. Brachial artery blood flow velocity and diameter were measured for a total of 12 min during each of the exercise sessions. Both anterograde blood flow (MOD: 191.3 ± 80.3 mL/min, HIIE: 153.9 ± 67.5 mL/min, p = 0.03) and shear rate (MOD: 203.5 ± 78.1 s−1, HIIE: 170.8 ± 55.5 s−1, p = 0.04) were higher during MOD compared to HIIE. Both retrograde blood flow (MOD: −48.7 ± 21.3 mL/min, HIIE: −63.9 ± 23.3 cm/s, p < 0.01) and shear rate (MOD: −51.5 ± 19.8 s−1, HIIE: −73.8 ± 28.4 s−1, p < 0.01) were of greater magnitude during HIIE compared to MOD. During exercise, brachial artery diameter (p = 0.34) did not differ between HIIE and MOD. Continuous moderate cycling exercise leads to higher brachial artery anterograde shear rate and blood flow, but lower retrograde shear rate and blood flow when compared to high-intensity interval exercise. These differences during exercise in blood flow characteristics could shed light on the differing chronic adaptations to these two types of exercise.

[Objective] This study was aimed at exploring the influence of nearsurface coverage formed by the collapse of flexible vegetation in reducing runoff and erosion yield, and in modulating the hydraulic properties of surface runoff. [Methods] Based on fundamental principles of fluid mechanics and hydraulics, the erosion patterns and hydrodynamic characteristics under lodged flexible vegetation were systemically investigated through indoor hydrodynamic experiments across five levels of coverage, five slope gradients, and three flow rates. [Results] (1) The distribution of erosion volume demonstrated an initial increase followed by a decrease with the increment of slope angle, with the influence of flow rate on the erosion process being more pronounced at steeper slopes. (2) Corresponding to an increase in the coverage of flexible vegetation, and taking 50% coverage as a threshold, the erosion volume generally exhibited a trend of initial reduction followed by an increase. (3) The average flow velocity (v) decreased with increasing vegetative coverage, with the rate of decline becoming gradual as coverage intensified. The variation in Froude number (Fr) mirrored the trend in average flow velocity. The friction coefficient (f) was positively linear correlated with coverage and decreased with an increase in slope gradient; the Reynolds number (Re) demonstrated a higher sensitivity to soil erosion compared to Fr, v, and f. (4) With the increase in vegetation coverage, morphological shear stress intensified (while particle shear stress diminished), playing a pivotal role in the changes in total shear stress, which was positively correlated with vegetation coverage. [Conclusion] The study establishes a solid theoretical foundation for the erosion patterns of slope flow vegetation and facilitates the expansion of open channel hydraulic theories in the realm of slope flows.

In vitro models of kidneys have limited effectiveness owing to the complex structure and functions of the kidney when compared with other organs. Therefore many renal function evaluations are currently being carried out through animal experiments. In contrast, efforts are being made to apply biomimetic systems, such as organ-on-a-chip, which is based on microfluidic device technology, to serve as an in vitro model for the kidney. These systems aimed to recreate a physiological cultivation environment. This review has provided an overview of organ-on-a-chip research focused on glomeruli and tubules as in vitro models for the kidney and discusses future prospects.

PURPOSE Laminar blood flow is known to play a critical role in maintaining endothelial homeostasis in blood vessels. It exerts a shear stress on the endothelial cells (ECs), which is essential for the regulation of various vascular functions. In this study, the effects of laminar blood flow-induced enhanced endothelial homeostasis on the maintenance of vascular function were investigated. METHODS Human umbilical vein endothelial cells (HUVECs) were employed to study gene expression associated with vessel dilation and angiogenesis in response to varying shear stress levels. To assess angiogenesis, experimental mice participated in voluntary wheel running for 16 weeks. To evaluate the vascular autophagic function, the six weeks old C57BL/6 mice underwent an hour of forced treadmill running for 10 weeks. The resulting gene expression was evaluated through western blotting and quantitative real-time polymerase chain reaction (qRT-PCR). RESULTS Disturbed flow resulting from partial ligation surgery in the mice's carotid artery led to a decrease in angiogenic capacity compared to the laminar flow observed in ex vivo sprouting assays. Cultured HUVECs exhibited a significant increase in VEGF expression when exposed to increased durations of 20 dyne/cm² laminar shear stress (LSS). Following a 10-week treadmill exercise regimen, ECs in the carotid arteries of mice showed a significant increase in the expression of autophagic genes, such as LC3II, Atg3, and Atg7, which was not observed in smooth muscle cells (SMCs). LSS was found to boost the expression of both total and phosphorylated eNOS, genes involved in vascular dilation regulation, specifically in ECs. CONCLUSIONS These findings suggest that laminar blood flow sustains vascular function, such as angiogenic capacity, through the enhancement of endothelial homeostasis.

One of the structures for regulating the water level in the irrigation and drainage ducts is the lopac gates, which are proposed as a structure for regulating and controlling the flow level. In this study, a new design of this type of structure has been proposed in which the gates are placed next to each other in pairs, and they are called multiple lopac gates. The objective of this research is to investigate the effective hydraulic parameters of the proposed structure and compare it in a case where a gate is used under the same conditions. All the simulations were modeled with 3 amounts of opening 30, 45, and 60 degrees and at 3 flow rates of 20, 40, and 60 liters per second and using Flow3d software, in these simulations, the number of mesh cells is 1000000 and RNG turbulence model is used. The results showed that the maximum shear stress was reduced by an average of 38% compared to the single gate mode in most tests at different openings and flow rates using multiple lopac gates, and the largest amount of this reduction was related to the opening of 45 degrees, and the flow rate is 40 liters per second with a value of 76%. Also, the forces acting on the gate at different flow rates and openings will be reduced by 150% on average. In the qualitative investigation of flow vortices, the investigations also showed that vortex range, length, and strength are reduced compared to the single gate mode when two gates are used, and the number of vortices increases compared to when a single valve.

Metal fatigue is a problem in the use of metals in their applications, especially when they are exposed to cyclic or repetitive loads. This study analyzes the effect of round, rectangular and spherical cross-sections on fatigue failure of ST 60 steel. By providing a fatigue test load of 150 N and a rotating speed of 1500 rpm and a test specimen installation position with a distance of 70 cm, it was found that the round cross-section broke when experiencing 26,471 cycles, the rectangular cross-sectional shape broke when experiencing 115,515 cycles and the hollow round shape broke when experiencing 201,983 cycles. The largest shear stress is generated by a spherical cross-section with a value of 247.7 N/mm2 and the lowest is by a material with a hollow spherical cross-section with a value of 194.478 N/mm2. Normal stress and the highest shear stress are produced specimens with a spherical cross-sectional shape, this is because the spherical cross-section has a tendency to spread normal stress evenly over its surface.

The sudden exposure of venous endothelial cells (vECs) to arterial fluid shear stress (FSS) is thought to be a major contributor to coronary artery bypass vein graft failure (VGF). However, the effects of arterial FSS on the vEC secretome are poorly characterised. We propose that analysis of the vEC secretome may reveal potential therapeutic approaches to suppress VGF. Human umbilical vein endothelial cells (HUVECs) pre-conditioned to venous FSS (18 h; 1.5 dynes/cm2) were exposed to venous or arterial FSS (15 dynes/cm2) for 24 h. Tandem Mass Tagging proteomic analysis of the vEC secretome identified significantly increased fibroleukin (FGL2) in conditioned media from HUVECs exposed to arterial FSS. This increase was validated by Western blotting. Application of the NFκB inhibitor BAY 11-7085 (1 µM) following pre-conditioning reduced FGL2 release from vECs exposed to arterial FSS. Exposure of vECs to arterial FSS increased apoptosis, measured by active cleaved caspase-3 (CC3) immunocytochemistry, which was likewise elevated in HUVECs treated with recombinant FGL2 (20 ng/mL) for 24 h under static conditions. To determine the mechanism of FGL2-induced apoptosis, HUVECs were pre-treated with a blocking antibody to FcγRIIB, a receptor FGL2 is proposed to interact with, which reduced CC3 levels. In conclusion, our findings indicate that the exposure of vECs to arterial FSS results in increased release of FGL2 via NFκB signalling, which promotes endothelial apoptosis via FcγRIIB signalling. Therefore, the inhibition of FGL2/FcγRIIB signalling may provide a novel approach to reduce arterial FSS-induced vEC apoptosis in vein grafts and suppress VGF. [ABSTRACT FROM AUTHOR]

The velocity of an unsteady flow of a viscous fluid of the second-grade MHD-type enclosed between two parallel side walls perpendicular to a plate was obtained by applying the integral transformation. The fluid is required to move by the plate, which over time t = 0 + subjected the fluid to shear stress. The solutions satisfy the given equation as well as the boundary and initial conditions, and they were separated into two types: steady state and transient state. Furthermore, through h → ∞ , we are able to recover the results found in the literature for motion across an infinite plate. Graphs depict the effect of the side walls and the time it takes to reach the steady state. The solutions are shown in graphs and discussed physically to examine the impact of different flow parameters. It is found that the fluid velocity decreases with an increasing fractional parameter β and second-grade parameter α. Also, it is noticed that the fluid velocity decreases with increasing values of Reynolds number and effective permeability. Numerous industrial products, including honey, paints, varnishes, coffee, chocolate and jelly, use this type of fluid flow concept. [ABSTRACT FROM AUTHOR]

Shear stress during bioreactor cultivation has significant impact on cell health, growth, and fate. Mammalian cells, such as T cells and stem cells, in next-generation cell therapies are especially more sensitive to shear stress present in their culture environment than bacteria. Therefore, a base knowledge about the shear stress imposed by the bioprocesses is needed to optimize the process parameters and enhance cell growth and yield. However, typical computational flow dynamics modeling or PCR-based assays have several limitations. Implementing and interpreting computational modeling often requires technical specialties and also relies on many simplifications in modeling. PCR-based assays evaluating changes in gene expression involve cumbersome sample preparation with the use of advanced lab equipment and technicians, hampering rapid and straightforward assessment of shear stress. Here, we developed a simple, cell-based shear stress sensor for measuring shear stress levels in different bioreactor types and operating conditions. We engineered a CHO-DG44 cell line to make its stress sensitive promoter EGR-1 control GFP expression. Subsequently, the stressed CHO cells were transferred into a 96 well plate, and their GFP levels (population mean fluorescence) were monitored using a cell analysis instrument (Incucyte®, Sartorius Stedim Biotech) over 24 hours. After conducting sensor characterization, which included chemical induced stress and fluid shear stress, and stability investigation, we tested the shear stress sensor in the Ambr® 250 bioreactor vessels (Sartorius Stedim Biotech) with different impeller and vessel designs. The results showed that the CHO cell-based shear stress sensors expressed higher GFP levels in response to higher shear stress magnitude or exposure time. These sensors are useful tools to assess shear stress imposed by bioreactor conditions and can facilitate the design of various bioreactor vessels with a low shear stress profile. [Display omitted] • First report on CHO cell-based fluid shear stress sensor in bioprocessing. • Sensor measures overall shear stress using conventional fluorescence microscopy. • Evaluated shear stress levels in commercial bioreactors. • Useful for designing vessels and impellers with low shear profile. [ABSTRACT FROM AUTHOR]

Iatrogenic aortic dissection is a rare but life-threatening complication of coronary artery bypass surgery. We report a case with incidentally detected iatrogenic aortic dissection related to aorta cross-clamping that was successfully managed with watchful follow-up. The decision making was based on 3-dimensional holographic and fluid dynamic analysis guidance. [ABSTRACT FROM AUTHOR]

The global population growth and increasing energy demand pose challenges to the Oil and Gas industry, leading to increased exploration and production in offshore and deep-sea areas. Offshore oilfields in colder regions produce crude oils with higher wax content, causing wax deposition and flow assurance issues in pipelines. Nanoparticle inhibitors can mitigate wax deposition in pipelines. In this study, the performance of zinc oxide nanoparticle is evaluated by measurement of degree of viscosity reduction and wax deposition of a Niger Delta crude oil sample. Wax deposition is determined by cold finger technique. 10g of zinc oxide (ZnO) nanoparticle is mixed in 500mL of crude oil sample. From this experiment, it was observed that at 2rpm (revolutions per minute), the degree of viscosity reduction (DVR) was 31% at 10°C and 3% at 15%. Increase in crude oil temperature enhanced the viscosity of the blank sample and the sample blended with ZnO nanoparticle. However, at lower temperatures of 10 and 15C, the viscosity of the blank crude increased. higher, indicating a poor performance of ZnO on the viscosity of the crude oil sample. The addition of 10g of ZnO nanoparticle had more cumulative wax deposit of 16.76g than the blank crude having a cumulative wax deposit in the cold finger as 14.32g. This implies that 10g nano ZnO did not prevent or reduce the wax deposition in the cold finger, but it was efficient at improving the viscosity and flowability of the Niger Delta crude sample. [ABSTRACT FROM AUTHOR]