Increase In Shear Stress Research Articles

Filtration performance of biofilm membrane bioreactor: Fouling control by threshold flux operation

Membrane fouling is the major factor that restricts the furtherly widespread use of membrane bioreactor (MBR). As a new generation of MBR, biofilm membrane bioreactor (BF-MBR) demonstrates high treatment efficiency and low sludge growth rate, however the filtration performance improvement and membrane fouling control are still the challenges for its further development. This work investigated the filtration performance using resistance in series model and membrane fouling control via threshold flux for BF-MBR. At first, the flux behavior and filtration resistance under various operating conditions, including agitation speed, membrane and TMP, were explored by resistance in series model. Because of the desirable anti-fouling capacity, UP100 and UP030 had the high threshold flux (100 and 90 L m−2 h−1) and low irreversible fouling resistance (1 and 1.3 × 10−10 m-1). Higher shear stress produced by higher agitation speed could reduce membrane fouling, while greatly promote the threshold flux (138 L m−2 h−1) and membrane cleaning efficiency (96%). Moreover, increasing shear stress or selecting membrane with large pore size could decrease the fouling rate and raise the threshold flux. As for TMP, high TMP reduced the removal rate for organic and nutrient, and enhanced the irreversible fouling. Besides, the aerobic-BF-MBR (101 L m−2 h−1 and 1.3 × 10−10 m-1) with lower foulant concentration had a better filtration performance than anoxic-BF-MBR (90 L m−2 h−1 and 1.5 × 10−10 m-1). Additionally, the long-term tests with 10 cycles were conducted to evaluate the industrial application value of BF-MBR (45–58 L m−2 h−1). This work provides the technical support for sustainable filtration performance of BF-MBR.

Does spinopelvic alignment affect femoral head cartilage and the proximal femoral physis in slipped capital femoral epiphysis? A finite element analysis

BackgroundSlipped capital femoral epiphysis is a prevalent pediatric hip disorder. Recent studies suggest the spine's sagittal profile may influence the proximal femoral growth plate's slippage, an aspect not extensively explored. This study utilizes finite element analysis to investigate how various spinopelvic alignments affect shear stress and growth plate slip. MethodsA finite element model was developed from CT scans of a healthy adult male lumbar spine, pelvis, and femurs. The model was subjected to various sagittal alignments through reorientation. Simulations of two-leg stance, one-leg stance, walking heel strike, ascending stairs heel strike, and descending stairs heel strike were conducted. Parameters measured included hip joint contact area, stress, and maximum growth plate Tresca (shear) stress. FindingsPosterior pelvic tilt cases indicated larger shear stresses compared to the anterior pelvic tilt variants except in two leg stance. Two leg stance resulted in decreases in the posterior tilted pelvi variants hip contact and growth plate Tresca stress compared to anterior tilted pelvi, however a combination of posterior pelvic tilt and high pelvic incidence indicated larger shear stresses on the growth plate. One leg stance and heal strike resulted in higher shear stress on the growth plate in posterior pelvic tilt variants compared to anterior pelvic tilt, with a combination of posterior pelvic tilt and high pelvic incidence resulting in the largest shear. InterpretationOur findings suggest that posterior pelvic tilt and high pelvic incidence may lead to increased shear stress at the growth plate. Activities performed in patients with these alignments may predispose to biomechanical loading that shears the growth plate, potentially leading to slip.

Torsional fatigue behaviour and damage mechanisms of martensitic spring steel in the HCF regime

This study investigates the fatigue behaviour and damage mechanisms of the martensitic spring steel SAE 9254, with emphasis on short crack propagation. Shear stress-controlled torsional fatigue tests are performed at stress ratio R = -1 and test frequency f = 79 Hz using structure-sensitive measurement techniques to detect the relevant damage mechanisms. An in-situ torsional fatigue testing device is applied for shear-controlled fatigue tests at two amplitudes of the torsion angle using R = –1 and f = 5 Hz, and the microstructural-dependent short crack propagation path is documented by means of confocal laser microscopy and electron backscattering analysis. It is found that the early development of fatigue damage is characterised by the formation of slip bands, which serve as crack initiation sites. In this process, crack initiation occurs preferentially at or near prior austenite grain boundaries. Furthermore, prior austenite grain boundaries were identified as obstacles for the propagation of short cracks, because of the change of the crystallographic orientation leading to an oscillating propagation rate of short cracks. The short crack density ρCD, which is an important parameter for fatigue damage, is rapidly growing with increasing shear stress amplitude ΔτT/2 and reveals a stress type specific behaviour.

Bearing Capacity Characteristic Analysis of Anti-floating Bolts in Unsaturated Soil Based on Mindlin Solution

AbstractBased on Mindlin solution and the theory of unsaturated soil mechanics, the theoretical solutions of shear stress and axial force distribution in the elastic stage of full-length binding-type anti-floating bolts were derived, and the bearing capacity characteristics of such bolts and the influencing factors were analyzed. In this paper, the design parameters of anti-floating anchor in a negative two-floor basement of a commercial square are substituted into the formula derived in this paper. The results show that, in unsaturated soil, the shear stress and axial force of the full-length bonded anti-floating anchor are distributed along the total length of the anchor, but neutral points appear in both of them, which is mainly due to the reduction of the axial force and shear stress of the anti-floating anchor caused by the matric suction. The formula derived in this paper is used to analyze the factors affecting the bearing capacity of anti-floating anchor bolt in unsaturated soil. The results show that: the greater the elastic modulus of soil mass, the greater the peak value of shear stress curve, the closer the peak value is to the head of anchor bolt, and the greater the axial force decline rate. With the increase of anchor solid diameter D, the peak value of shear stress decreases, the peak value moves backward, the neutral point moves forward, the negative shear stress value increases, the decline rate of axial force distribution curve decreases, but the negative axial force increases. With the increase of the additional shear stress τ0, the peak value of the shear stress curve decreases, the peak value moves to the hole of the anchor rod, the neutral point moves to the hole, the negative shear stress increases, the decline rate of the axial force distribution curve increases, and the negative axial force increases.

The effect of grain boundaries and precipitates on the mechanical behavior of the refractory compositionally complex alloy NbMoCrTiAl

Refractory compositionally complex alloys (CCAs) have been found to exhibit promising high-temperature properties. However, the brittleness of most CCAs at room temperature limits their application. To understand the influence of microstructure on the deformation behavior of these alloys, we conducted micromechanical experiments, including nanoindentation and micropillar compression tests, on a representative NbMoCrTiAl alloy at room temperature. The indentation at the grain boundaries showed increased shear stress and hardness compared to the matrix (ordered B2 crystal structure) due to the presence of local intermetallic precipitates (C14 and A15 phases). Although the NbMoCrTiAl alloy exhibits no ductility at the millimeter scale as shown in previous studies, the micropillars at the grain boundaries, which were decorated with precipitates, demonstrated higher yield strength and significant plastic strain >30% at room temperature. Numerous slip lines were observed, while cracks and fracture occurred at higher levels of deformation. The grain boundaries with precipitates increased the probability of crack initiation and propagation, but they did not necessarily lead to catastrophic failure of the pillars.

Two-dimensional rheo-optical measurement system to study dynamics and structure of complex fluids

Abstract We have developed a novel rheo-optical measurement system based on two-dimensional polarization analysis, which can evaluate the rheological properties and structure of a complex fluid simultaneously. To assess the utility of the system, we used it to investigate the relationship between yield behavior and structural evolution in a TEMPO-oxidized cellulose nanofiber (T-CNF) suspension, which is a yield-stress fluid that has been actively studied in recent years. To analyze the structural evolution of a T-CNF suspension, stress-ramp tests were conducted. A two-step yield behavior was observed, and distributions of retardation and orientation axis varied dramatically with increasing shear stress. In particular, different distributions were observed in the three regions: after the first yield point, before the second yield point, and after the second yield point. In experiments with a low-concentration T-CNF suspension that exhibits no yield behavior, the retardation increased monotonically with increasing shear stress, and its distribution was uniform. It was demonstrated that the yield behavior and related structures can be analyzed from these results. More detailed structural mechanisms require various rheological tests using the developed system. However, the present insights demonstrate the valuable information provided by the developed rheo-optical measurement system, contributing essential knowledge for applications in various fields.

Mixed convection of ferrohydrodynamics magnetized hybrid ferrofluid on a slip-permeable stretching sheet

Mixed convection significantly affects fluid flow and heat transfer in manufacturing and engineering. This study investigates it in a ferrohydrodynamics magnetized hybrid ferrofluid on a slip stretching sheet affected by suction and injection. Using the modified Tiwari and Das model, the behavior of the hybrid ferrofluid, magnetite ferrite ( F e 3 O 4 ) and cobalt ferrite ( CoF e 2 O 4 ) based-water and ethylene glycol are explored. The governing partial differential equations are simplified via a similarity technique and solved using the Keller box method. Forced convection reduces velocity profile and shear stress more rapidly than mixed and natural convection, exhibiting distinct thermal field and Nusselt number patterns. Injection increases shear stress by 71.98%, 83%, and 87.08% under forced, mixed, and natural convection, while suction raises it by 25.96%, 28.50%, and 28.53%, respectively. Under suction, natural convection drop by 5.12% Nusselt number, slightly less than forced (5.36%) and mixed convection (5.15%). Ferrohydrodynamics significantly influences flow and heat transfer.

Hydraulic investigation of flow and bed load transport in diverging compound channels with rigid and flexible vegetation

Floodplains are really important for the environment as they provide various functions for waterways, including ecological, hydrological, and geomorphic ones. During overbank flows, there are complex hydrodynamic conditions that occur as water interacts with the rough floodplain vegetation and drag forces due to the vegetation that changes the flow pattern. However, we still don't fully understand how floodplain vegetation influences channel-altering hydrodynamic forces and sediment transport. To address this, we conducted flume experiments and measured flow pattern and sediment transport under varied floodplain geometry and rigid and flexible conditions. For this purpose, a physical model was constructed in the laboratory, in which plastic rods with a diameter of 10 mm will be used as trees, and artificial grass will be grass vegetation. Thus, 36 experiments were conducted in which the sedimentation and hydraulic parameters of the flow were calculated by measuring the flow velocity, water surface, and sediment transport rate. The results show that in the floodplain with dense (rigid and flexible) vegetation, the friction coefficient (f) is even 1.5 times higher than in the floodplain without vegetation. The parameters such as flow velocity, bed shear stress and Darcy Weissbach friction coefficient increase in the vertical plane between the main channel and floodplains due to the difference in roughness between the main channel and floodplains. In addition, in the main channel, the flow resistance is almost constant and does not depend on the vegetation density. The Darcy-Weissbach friction coefficient is greatly increased in the presence of grass and tree vegetation on the floodplain, and the larger contribution of f is due to the grass vegetation. The results also showed the sediment transport rate has a direct relationship with the angle of divergence and density of vegetation and an inverse relationship with the relative depth of the flow. Therefore, as the sediment transport rate decreases in the diverging compound channel, the wavelength and height of the dunes increase. At smaller divergence angles, the dunes tend to the top of the zero line (the level of the sediments before the formation of the bed form). In the presence of vegetation, due to the increase in the roughness ratio of the floodplain to the main channel, the contribution of the main channel to the flow rate increases. As a result, the sediment transport rate increases.

Effect of Faba Bean Isolate and Microbial Transglutaminase on Rheological Properties of Pork Myofibrillar Protein Gel and Physicochemical and Textural Properties of Reduced-Salt, Low-Fat Pork Model Sausages.

The study was performed to determine the effect of faba bean protein isolate (FBPI) alone or in combination with microbial transglutaminase (MTG) on the rheological properties of pork myofibrillar protein gel (MPG), and physiochemical and textural properties of reduced-salt, low-fat pork model sausages (LFMSs). The cooking yields of MPGs with MTG or FBPI alone decreased and increased, respectively. However, the combination of FBPI and MTG was similar to the control (CTL) without FBPI or MTG. Gel strength values of MPG added with both FBPI and MTG were higher than treatments with FBPI or MTG alone. The hydrophobicity values of CTL were lower than those of MPG with FBPI alone, whereas the addition of MTG decreased the hydrophobicity of MPGs. The incorporation of FBPI alone or in combination with MTG decreased sulfhydryl groups (p<0.05). Shear stress values of MPGs with MTG tended to be higher than those of non-MTG treatments at all shear rates, and the addition of FBPI into MPGs increased shear stress values. Reduced-salt (1.0%) LFMSs with FBPI alone or combined with MTG had both lower cooking loss and expressible moisture values than those of CTL and similar values to the reference sample (REF, 1.5% salt). Textural properties of reduced-salt LFMSs with FBPI or MTG were similar to those of REF. These results demonstrated that the combination of FBPI and MTG could improve the water binding capacity and textural properties of pork MPGs and LFMSs and might be suitable for application in the development of healthier meat products.

Fibulin-5 Is Required for Small Artery Development and Function

Introduction: Fibulins are a family of eight extracellular matrix proteins with diverse functions. Fibulin-4 and -5 (FBLN-4 and -5), in particular, have been shown to be important for elastic fiber assembly. Mutations in each of the genes lead to cutis laxa, a syndrome characterized by loose skin with variable organ involvement, particularly in the vasculature, lungs and skeleton. We recently characterized a mouse model carrying a disease-causing mutation in Fbln4 (E57K) and, contrary to conduit arteries that had elastic fiber fragmentation and stiffness, Fbln4E57K resistance arteries were structurally intact. Functionally however, Fbln4E57K mesenteric arteries exhibited endothelial dysfunction secondary to increased shear stress from large artery stiffness. Loss of FBLN5 has been shown to lead to elastic fiber fragmentation in conduit arteries, but the consequences of its loss on resistance arteries are unknown. Therefore, the objectives of this study were to determine the structural and functional consequences of FBLN5 loss on resistance arteries. Methods: We utilized adult Fbln5 knock-out (KO) mice and examined the ultrastructure of renal and mesenteric arteries via transmission electron microscopy. Functionally, using pressure myography, we characterized the myogenic tone and reactivity of Fbln5 KO and littermate control third-order mesenteric arteries to various vasoactive substances including acetylcholine, papaverine, angiotensin II, phenylephrine and potassium chloride. Results: While the internal elastic lamina (IEL) of Fbln5KO mice resistance arteries was largely intact, the external elastic lamina (EEL) was nearly absent. Similar to Fbln4E57K mice, Fbln5KO mesenteric arteries exhibited impaired endothelial-dependent vasorelaxation, likely secondary to proximal large artery stiffness. Unlike Fbln4E57K mesenteric arteries however, Fbln5 KO mesenteric arteries exhibited increased myogenic tone as well as a hypercontractile response to angiotensin II and potassium chloride, but not to phenylephrine. Conclusions: In addition to highlighting differences in the requirements for elastic fiber assembly along the arterial tree, these data emphasize the differential contribution of FBLN4 and FBLN5 to IEL vs. EEL in resistance arteries and suggest pathway-specific changes in smooth muscle cell contractility secondary to FBLN5 deficiency. This work was supported by the Washington University Pediatric Nephrology Research Core Pilot Grant Program to CMH. Funds were also provided by The Department of Pediatrics at Washington University in St. Louis School of Medicine to CMH. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

DOES ENDOTHELIAL FUNCTION DIFFER AMONG SEXES IN PATIENTS WITH DIABETES OR KIDNEY DISEASE?

Objective: Endothelial dysfunction is a known driver of disease progression in both type 2 diabetes mellitus (T2DM) and kidney disease. Brachial artery flow-mediated dilation (FMD), representing endothelium-dependent nitric oxide-mediated dilation in response to increased shear stress, is considered gold standard to quantify macrovascular dysfunction non-invasively. As evidence is mounting that men are more likely to suffer from macrovascular dysfunction than women, we hypothesized that this would be reflected in patient populations with T2DM and/or kidney disease. Design and method: Preliminary baseline data was collected from 2 ongoing randomized controlled trials in patients with T2DM and in kidney transplant recipients (KTRs) 3 months post-transplantation. FMD was assessed with the semi-automated UNEX EF device under standardized conditions. Biochemical analyses were done using routine techniques. Images were manually analyzed by a single researcher (MR) using PCAnalysis software (version 1.0.14). Results: Twenty-five subjects, 13 with T2DM and 12 KTRs were included. As expected, patients with T2DM had a higher BMI, higher HbA1c but higher eGFR compared to KTRs (Table 1). Compared to KTRs, patients with T2DM presented with a significantly worse FMD (FMD= 4.50% [IQR=5.77]) vs 10.88% [6.48]). Overall, no significant difference in FMD between men and women was found (p=0.11), but higher values could be observed in females (FMD= 9.08% [IQR=6.97] vs 4.50% [7.88]). As depicted in Figure 2, this tendency was also observed in the 2 subgroups: KTRs (M: FMD = 9.07% [IQR=9.62] | F: 11.92% [5.16]) and T2DM (M: FMD = 3.90% [IQR=5.00%] | F: 7.09% [6.83]). Conclusions: Although no significant differences in vascular function between sexes were detected, our preliminary data showed a tendency for higher FMD-values in women; both in T2DM and KTRs. This supports the statement that male subjects seem to suffer more from macrovascular dysfunction. Further research is needed to elucidate the underlying pathways via which sex impacts the disease process in T2DM and kidney disease and to evaluate how personalized preventive lifestyle measures might differentially impact on outcome.

Solute clustering and its role in a titanium alloy made by laser powder bed fusion

In recent years, atomic clusters and composition undulation have been observed in a number of concentrated solid-solution alloys and were found to be beneficial for strength-ductility synergy. Some reports are also available on the observation of atomic clusters in body-centred cubic metastable β titanium alloys but the role of these atomic clusters in mechanical property development is unclear. In this study, we report the formation of solute atomic clusters in an additively manufactured and solution-treated metastable titanium alloy and investigate their role in deformation and strengthening mechanisms. It was found that the atomic clusters together with ultrafine ω precipitates present in the material effectively pin dislocation motion and contribute to an ultrahigh yield strength. The interaction between dislocations and solute atomic clusters leads to an increased shear stress necessary for dislocation motion. The atomic clusters and the resulting chemical undulation generate pronounced atomic strain fluctuations and distortions with alternating tensile and compressive strain fields, which lead to large local internal stresses and thus resistance to dislocation glide. Cross slip has also been frequently observed in the additively manufactured and solution-treated metastable titanium alloys, which is beneficial for strain hardening and ductility. We also reveal that thermal cycling in the alloy can lead to a significant influence on the microstructural evolution. During solidification and cooling upon laser powder bed fusion, only β and athermal ω precipitates form. With repetitive thermal cycling, the microstructure transforms into α + β grains together with isothermal ω particles. The present findings suggest that solute atom clustering can be introduced through proper selection of solute elements, providing a new strengthening mechanism for titanium alloys.

Creep constitutive modeling of the shear strength of the permafrost-concrete interface considering the stress level at -1°C.

The shear creep characteristics of the contact surface between the permafrost and the structure play an important role in the study of the law of deformation and the measures for the prevention and control of pile foundations. In order to study the creep law and the development tendency of the contact surface between permafrost and concrete, it is necessary to establish an accurate creep model. In this study, based on the Nishihara model, a nonlinear element and damage factor D were introduced to establish an intrinsic model of permafrost-concrete contact surfaces considering the effect of shear stress. Creep tests with graded loading of concrete and frozen silt with different roughness at -1°C were conducted using a large stress-controlled shear apparatus. The adequacy of the model was checked using the test data and the regularity of the parameters of the model was investigated. The results show that the creep curves of the contact surface obtained with the improved Nishihara model agree well with the test results and can better describe the whole process of creep of the contact surface of frozen concrete. The analysis of the experimental data shows that: the roughness of the concrete has an inhibiting effect on the creep deformation of the contact surface, When the roughness R varies from 0 mm to 1.225 mm, the specimen corresponds to a long-term strength of 32.84 kPa to 34.57 kPa. For the same roughness and creep time, the creep deformation of the contact surface is more significant with the increasing shear stress τ. The results of the study can provide a theoretical basis for the design and numerical simulation of pile foundations in permafrost regions.

Shear and normal stresses of electroosmotic magnetized physiological nanofluid on curved artery with moderate Reynolds number: application on electroshock therapy

PurposeStudying the shear stress and pressure resulting on the walls of blood vessels, especially during high-pressure cases, which may lead to the explosion or rupture of these vessels, can also lead to the death of many patients. Therefore, it was necessary to try to control the shear and normal stresses on these veins through nanoparticles in the presence of some external forces, such as exposure to some electromagnetic shocks, to reduce the risk of high pressure and stress on those blood vessels. This study aims to examines the shear and normal stresses of electroosmotic-magnetized Sutterby Buongiorno’s nanofluid in a symmetric peristaltic channel with a moderate Reynolds number and curvature. The production of thermal radiation is also considered. Sutterby nanofluids equations of motion, energy equation, nanoparticles concentration, induced magnetic field and electric potential are calculated without approximation using small and long wavelengths with moderate Reynolds numbers.Design/methodology/approachThe Adomian decomposition method solves the nonlinear partial differential equations with related boundary conditions. Graphs and tables show flow features and biophysical factors like shear and normal stresses.FindingsThis study found that when curvature and a moderate Reynolds number are present, the non-Newtonian Sutterby fluid raises shear stress across all domains due to velocity decay, resulting in high shear stress. Additionally, modest mobility increases shear stress across all channel domains. The Sutterby parameter causes fluid motion resistance, which results in low energy generation and a decrease in the temperature distribution.Originality/valueEquations of motion, energy equation, nanoparticle concentration, induced magnetic field and electric potential for Sutterby nano-fluids are obtained without any approximation i.e. the authors take small and long wavelengths and also moderate Reynolds numbers.

The impact of small movements with dual lumen cannulae during venovenous extracorporeal membrane oxygenation: A computational fluid dynamics analysis

Background and objectivesVenovenous Extracorporeal Membrane Oxygenation (VV ECMO) provides respiratory support to patients with severe lung disease failing conventional medical therapy. An essential component of the ECMO circuit are the cannulas, which drain and return blood into the body. Despite being anchored to the patient to prevent accidental removal, minor cannula movements are common during ECMO. The clinical and haemodynamic consequences of these small movements are currently unclear. This study investigated the risk of thrombosis and recirculation caused by small movements of a dual lumen cannula (DLC) in an adult using computational fluid dynamics. MethodsThe 3D model of an AVALON Elite DLC (27 Fr) and a patient-specific vena cava and right atrium were generated for an adult patient on ECMO. The baseline cannula position was generated where the return jet enters the tricuspid valve. Alternative cannula positions were obtained by shifting the cannula 5 and 15 mm towards inferior (IVC) and superior (SVC) vena cava, respectively. ECMO settings of 4 L/min blood flow and pulsatile flow at SVC and IVC were applied. Recirculation was defined as a scalar value indicating the infused oxygenated blood inside the drainage lumen, while thrombosis risk was evaluated by shear stress, stagnation volume, washout, and turbulent kinetic energy. ResultsRecirculation for all models was less than 3.1 %. DLC movements between -5 to 15 mm increased shear stress and turbulence kinetic energy up to 24.7 % and 11.8 %, respectively, compared to the baseline cannula position leading to a higher predicted thrombosis risk. All models obtained a complete washout after nine seconds except for when the cannula migrated 15 mm into the SVC, indicating persisting stasis and circulating zones. ConclusionIn conclusion, small DLC movements were not associated with an increased risk of recirculation. However, they may increase the risk of thrombosis due to increased shear rate, turbulence, and slower washout of blood. Developing effective cannula securement devices may reduce this risk.

A tempo-spatial controllable microfluidic shear-stress generator for in-vitro mimicking of the thrombus

Pathological conditions linked to shear stress have been identified in hematological diseases, cardiovascular diseases, and cancer. These conditions often exhibit significantly elevated shear stress levels, surpassing 1000 dyn/cm2 in severely stenotic arteries. Heightened shear stress can induce mechanical harm to endothelial cells, potentially leading to bleeding and fatal consequences. However, current technology still grapples with limitations, including inadequate flexibility in simulating bodily shear stress environments, limited range of shear stress generation, and spatial and temporal adaptability. Consequently, a comprehensive understanding of the mechanisms underlying the impact of shear stress on physiological and pathological conditions, like thrombosis, remains inadequate. To address these limitations, this study presents a microfluidic-based shear stress generation chip as a proposed solution. The chip achieves a substantial 929-fold variation in shear stress solely by adjusting the degree of constriction in branch channels after PDMS fabrication. Experiments demonstrated that a rapid increase in shear stress up to 1000 dyn/cm2 significantly detached 88.2% cells from the substrate. Long-term exposure (24 h) to shear stress levels below 8.3 dyn/cm2 did not significantly impact cell growth. Furthermore, cells exposed to shear stress levels equal to or greater than 8.3 dyn/cm2 exhibited significant alterations in aspect ratio and orientation, following a normal distribution. This microfluidic chip provides a reliable tool for investigating cellular responses to the wide-ranging shear stress existing in both physiological and pathological flow conditions.Graphical

Thermally stressed state of asphalt concrete layer on a metal base

The results of a finite element study of the thermally stressed and deformed states of a fragment of a two-layer bridge structure, consisting of a bearing metal orthotropic slab with a layer of asphalt concrete applied on it, are presented. It is believed that the materials of the layers are characterized by different thermomechanical parameters, which determine the inhomogeneity of the stress and strain fields. An analogue of these phenomena can be the effect of transformation in electric thermal relays of thermal action on a bimetallic plate with different coefficients of thermal linear expansion into its mechanical displacements, which are used to actuate the switch and switches. Using the method of computer modeling, it was found that these factors lead to the concentration of stresses and strains and changes in the stress-strain state in all elements of the bridge structure end are not taken into account in the modern practice of designing and operating bridges, as well as are one of the reasons for the premature destruction of asphalt concrete pavements. To eliminate these shortcomings, on the basis of finite element algorithms, a theoretical analysis of the thermally stressed state of a metal bridge slab with an asphalt concrete pavement at various ratios of their thicknesses is carried out. It is shown that an increase in the thickness of the upper layer can lead to an increase in shear and normal tensile stresses initiated in it. Therefore, when designing bridge structures, these features should be additionally taken into account.

Management of aortic valve insufficiency in patients with continuous-flow left ventricular assist device: a republication of the review published in Japanese Journal of Artificial Organs.

Since 2011, implantable ventricular assist devices have been a standard treatment for severe heart failure alongside heart transplantation in Japan. However, the limited availability of donors has led to a prolonged wait for transplants, now averaging 1719days, intensifying the issue of aortic insufficiency in patients with continuous flow ventricular assist devices. These devices limit the opening of the aortic valve, leading to sustained closure and increased shear stress, which accelerates valve degradation. Risk factors for aortic insufficiency include having a smaller body surface area, being of advanced age, and the presence of mild aortic insufficiency prior to device implantation. In patients presenting with mild or moderate aortic regurgitation at the time of ventricular assist device implantation, interventions such as aortic valve repair or bioprosthetic valve replacement are performed with the aim of halting its progression. The choice of surgical procedure should be tailored to each patient's individual condition. The management of de novo aortic insufficiency in patients with continuous flow ventricular assist devices remains challenging, with no clear consensus on when to intervene. Interventions for significant aortic insufficiency typically consider the patient's symptoms and aortic insufficiency severity. De novo aortic insufficiency progression in continuous flow ventricular assist devices patients necessitates careful monitoring and intervention based on individual patient assessments and valve condition. This review was created based on a translation of the Japanese review written in the Japanese Journal of Artificial Organs in 2023 (Vol. 52, No. 1, pp. 77-80), with some modifications.

Hemodynamics in nutcracker syndrome: implications for diagnosis.

Nutcracker syndrome is a disease characterized by complex symptoms, making its diagnosis challenging and often delayed, often resulting in a painful experience for the patients. This study aimed to investigate the pathogenesis of nutcracker syndrome through the perspective of hemodynamics by simulating blood flow with varying compression degrees of the left renal vein. 3D patient-specific vascular models of the abdominal aorta, superior mesenteric artery and left renal vein were constructed based on CT images of patients suspected of having nutcracker syndrome. A hemodynamic simulation was then conducted using computational fluid dynamics to identify the correlation between alterations in hemodynamic parameters and varying degrees of compression. The study indicated the presence of anevident gradient in velocity distribution over the left renal vein with relatively high degrees of stenosis (α ≤ 50°), with maximum velocity in the central region of the stenosis. Additionally, when the compression degree of the left renal vein increases, the pressure distribution of the left renal vein presents an increasing number of gradient layers. Furthermore, the wall shear stress shows a correlation with the variation of blood flow velocity, i.e., the increase of wall shear stress correlates with the acceleration of the blood flow velocity. Using computational fluid dynamics as a non-invasive instrument to obtain the hemodynamic characteristics of nutcracker syndrome is feasible and could provide insights into the pathological mechanisms of thenutcracker syndrome supporting clinicians in diagnosis.

Investigation on the flexural–tensile behaviour of CFRP tendon composite anchorage system

The cable at the anchorage end is in a bending–tension condition in service due to the variable loads. A new composite anchorage system was proposed to study the flexural–tensile behaviour of the anchorage system with CFRP tendon. Four groups of single-tendon composite anchorage and three groups of five-tendon composite anchorage with bend restrictor were tested. Besides, one group of five-tendon composite anchorage without bend restrictor was tested as a control group. The effects of the bending angle, inner cone angle of the steel barrel and pre-tension force on the flexural–tensile behaviour of the anchorage system were investigated. The internal force state of the tendon inducing different failure modes was analysed. A finite element method was used to analyse the failure mechanism of the anchorage system under the bending–tension condition. Moreover, the flexural–tensile behaviours of the anchorage systems with different elastic moduli of the bonding medium were compared. Results showed that the efficiency coefficients of the composite anchorage with multi-tendon exceeded 0.9 when the end bending angle was less than 4.2°. The setting of the bending restrictor improves the flexural–tensile bearing capacity of the anchorage system and increases the maximum allowable bending angle. A larger bending angle will lead to a faster increase in the transverse shear stress at the loading end. Furthermore, increasing the pre-tension force can prompt the cooperation ability of the tendons and reduce the ultimate slips, thus improving the ultimate load-bearing capacity of the anchorage. The increase in the elastic modulus remarkably reduces the slip of the tendon, but increases the shear stress at the loading end under the bending–tension condition.