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Sedimentation in river and drainage systems frequently increases flood risks, making the study of particle dispersion crucial for effective flood damage control. In the present research, the transport of fine settling particles in a laminar, periodic flow through an open channel is analytically investigated using the multi-scale homogenization method. To investigate how settling velocity affects the dispersion process of fine particles in a tidal wetland, Dhar et al. (2022) studied the dispersion coefficient and mean concentration of the settling particles applying the method of moments. The mean and transverse real concentration distributions of settling particles are analytically derived from the governing equation, and the influence of settling velocity, oscillation Reynolds number, and Schmidt number on the dispersivity and concentration profile of the settling particles is investigated. The results show a vertical non-uniformity of longitudinal concentration distribution due to the introduction of settling velocity. It is also observed that the sedimentation effect for purely oscillatory flow is negligibly small compared to that of the steady and oscillatory flow with a nonzero mean. Pulsatile behavior is observed in the difference rate profile between Taylor's mean and present mean concentration. The study sheds light on the behavior of settling particles and can be useful for understanding sedimentation and wastewater treatment processes. • Vertical variation for transport of sediment particles in a pulsatile laminar open channel flow is demonstrated. • The settling effect on concentration distribution is small for purely oscillatory flow. • The fine particles concentrated more near the source for tidal flow compared to other flow conditions. • The longitudinal spreading of particles decreases with increasing oscillatory Reynolds number and Schmidt number. • The flow geometry significantly influences the vertical variation rate of settling particles. [ABSTRACT FROM AUTHOR]

A detailed study of the effect of coarctation on the blood flow of the thoracic aorta was carried out by modeling the interaction between blood and the aortic wall. Fluid-structure interaction (FSI) simulations were performed on the thoracic aorta geometries of healthy and diseased patients obtained from medical images. The pulsating flow of non-Newtonian blood was set by the boundary condition for the velocity in the form of a periodic physiological wave depending on time. As a result, the parameters of blood flow and vessel deformation were evaluated. It is shown that the velocity value at the site of aortic narrowing increases and falls after the narrowing. In addition, it can be noted that the value of pressure in the healthy aorta was higher than in the aorta with CoA, but at the same time, the pressure in the CoA model increased after the coarctation zone. It was noted that the shear stresses for the two models showed little difference and WSS was overestimated in the diseased aorta. As can be seen from the obtained data, using numerical simulation, important characteristics were determined to assess the influence of the fluid-structure interaction during blood flow in the flexible stenotic thoracic aorta. [ABSTRACT FROM AUTHOR]

Understanding spermatozoa transportation in the human female cervical canal, particularly in relation to the fertilization process, holds significant physiological importance. Present paper accords with the assessment of the self-propelling sheet of spermatozoa (SPSS) between porous cervical walls continuously secreting viscoelastic mucus in the human cervical canal (HCC). Mathematical modelling of the biological model yielded two inhomogeneous partial differential equations. These partial differential equations along with Saffman slip conditions are solved for exact solutions. It is delineated that an increase in the Reynolds number, Jeffrey parameter, and slip parameter results in an increase in the propulsive velocity and mucus velocity. Conversely, an increase in Darcy number results in a decrease in both propulsive and mucus velocity. When the secreting velocity is constant, the propulsive velocity is maximal, and when the secreting velocity is exponential, it is minimal. Spermatozoa move through the Jeffrey fluid more quickly than they do in the Newtonian fluid. The propulsive velocity through the channel is higher than in unbounded domain. The propulsive velocity of the spermatozoa in cervical canal is approximately 80 μ m/s in particular environment. [ABSTRACT FROM AUTHOR]

This in vitro study aims at clarifying the relation between the oscillatory flow of cerebrospinal fluid (CSF) in the cerebral aqueduct, a narrow conduit connecting the third and fourth ventricles, and the corresponding interventricular pressure difference. Dimensional analysis is used in designing an anatomically correct scaled model of the aqueduct flow, with physical similarity maintained by adjusting the flow frequency and the properties of the working fluid. The time-varying pressure difference across the aqueduct corresponding to a given oscillatory flow rate is measured in parametric ranges covering the range of flow conditions commonly encountered in healthy subjects. Parametric dependences are delineated for the time-averaged pressure fluctuations and for the phase lag between the transaqueductal pressure difference and the flow rate, both having clinical relevance. The results are validated through comparisons with predictions obtained with a previously derived computational model. The parametric quantification in this study enables the derivation of a simple formula for the relation between the transaqueductal pressure and the stroke volume. This relationship can be useful in the quantification of transmantle pressure differences based on non-invasive magnetic-resonance-velocimetry measurements of aqueduct flow for investigation of CSF-related disorders. [Display omitted] • In vitro experiments are used to quantify flow and pressure in the cerebral aqueduct. • The transaqueductal pressure is quantified as a function of the stroke volume. • The results are useful for non-invasive clinical evaluation of transmantle pressure. [ABSTRACT FROM AUTHOR]

The trans-radial approach for cardiac catheterization led to an increasing adoption of 5 French (F) catheters. We aim to evaluate reliability and reproducibility of coronary physiology assessment performed with 5F guiding catheter (GC). Physiological measurements were performed in a coronary flow simulator, which provides two pulsatile flows, the baseline and hyperaemic flows. Two screws, positioned proximally and distally to the distal sensor of a pressure-temperature guidewire, were used to determine various combinations of stenoses and distal obstructions, simulating different pathophysiological conditions. For each setting, 5 measurements of fractional flow reserve (FFR), coronary flow reserve (CFR) and index of microvascular resistance (IMR) were performed with 6F and 5F GCs. A total amount of 190 measurements were performed, 95 with 6F GC and 95 with 5F GC. Minimal differences between 6F and 5F GCs were detected for FFR [0.91 (IQR: 0.87–0.94) and 0.87 (IQR: 0.82–0.92) respectively, p < 0.001] and IMR (16.5 ± 8.8 and 15.4 ± 8.3 respectively, p = 0.001). Mean CFR was comparable between 6F and 5F GCs (3.6 ± 1.1 and 3.5 ± 0.7 respectively, p = 0.38). Misclassification rates were 1.0 %, 1.0 % and 0 % for FFR, CFR and IMR, respectively. According to Passing-Bablok analysis, an excellent agreement between 6F and 5F GCs was demonstrated for FFR and IMR, and a modest agreement for CFR. All measurements with 5F GC showed high reproducibility. In our in-vitro model, a complete physiological assessment including FFR, CFR and IMR resulted substantially comparable between 6F and 5F GCs. Further in-vivo analysis is required to support these findings. • Trans-radial access has increased the use of 5F guiding catheters (GC) for invasive physiology assessment • Complete assessment of invasive physiology with 5F GC has not been proven comparable to 6F yet • According to our findings, 5F GC allows for a reliable full physiology assessment with bolus thermodilution techniques [ABSTRACT FROM AUTHOR]

In vitro production of blood platelets for transfusion purposes is gaining interest. While platelet production is now possible on a laboratory scale, the challenge is to move towards industrial production. Attaining this goal calls for the development of platelet release devices capable of producing large quantities of platelets. To this end, we have developed a continuous-flow platelet release device composed of five spherical chambers each containing two calibrated cones placed in a staggered configuration. Following perfusion of proplatelet-bearing cultured megakaryocytes, the device achieves a high yield of about 100 bona-fide platelets/megakaryocyte, at a flow rate of ∼80 mL/min. Performances and operating conditions comply with the requirements of large-scale platelet production. Moreover, this device enabled an in-depth analysis of the flow regimes through Computational Fluid Dynamics (CFD). This revealed two new universal parameters to be taken into account for an optimal platelet release: i.e. a periodic hydrodynamic load and a sufficient accumulation of shear stress. An efficient 16 Pa.s shear stress accumulation is obtained in our system at a flow rate of 80 mL/min. [Display omitted] • Development of a cGMP and sterile ready-to-use platelet release device. • Platelet release device suitable for large-scale platelet production. • Production of bona fide platelets with a yield of 100 platelets/MK. • Hydrodynamic loading is a new flow parameter for efficient platelet release. • Shear stress accumulation is a new flow parameter for efficient platelet release. [ABSTRACT FROM AUTHOR]

• Most oscillatory physiological flows display a periodic time dependence characterized by a complex waveform. • Steady streaming driven by non-sinusoidal pressure gradients in wall-bounded flows is investigated by asymptotic and numerical methods. • The asymptotic predictions, derived for small stroke lengths, are in excellent agreement with the numerical results. • The steady streaming induced by pressure gradients derived from in-vivo MRI measurements in the spinal canal is computed. • Inter-frequency interactions are found to be more pronounced in cardiac-driven flow than in respiratory-driven flow. [Display omitted] The classical problem of secondary flow driven by a sinusoidally varying pressure gradient is extended here to address periodic pressure gradients of complex waveform, which are present in many oscillatory physiological flows. A slender two-dimensional wavy-walled channel is selected as a canonical model problem. Following standard steady-streaming analyses, valid for small values of the ratio ε of the stroke length of the pulsatile motion to the channel wavelength, the spatially periodic flow is described in terms of power-law expansions of ε , with the Womersley number assumed to be of order unity. The solution found at leading order involves a time-periodic velocity with a zero time-averaged value at any given point. As in the case of a sinusoidal pressure gradient, effects of inertia enter at the following order to induce a steady flow in the form of recirculating vortices with zero net flow rate. An improved two-term asymptotic description of this secondary flow is sought by carrying the analysis to the following order. It is found that, when the pressure gradient has a waveform with multiple harmonics, the resulting velocity corrections display a nonzero flow rate, not present in the single-frequency case, which enables stationary convective transport along the channel. Direct numerical simulations for values of ε of order unity are used to investigate effects of inertia and delineate the range of validity of the asymptotic limit ε ≪ 1. The comparisons of the time-averaged velocity obtained numerically with the two-term asymptotic description reveals that the latter remains remarkably accurate for values of ε exceeding 0.5. As an illustrative example, the results of the model problem are used to investigate the cerebrospinal-fluid flow driven along the spinal canal by the cardiac and respiratory cycles, characterized by markedly non-sinusoidal waveforms. [ABSTRACT FROM AUTHOR]

The influence of Thermophoresis and Brownian motion on the pulsing flow of nano-fluid (blood) through a curved artery with stenosis and post-stenotic dilatation in its interior is investigated numerically. The Herschel-Bulkley model of fluid dynamics accurately represents the fluid's rheology. By applying the mild stenosis condition, the highly coupled momentum, energy, and mass concentration equations can be modelled and reduced. Explicit finite differences methods are used to discretize and solve the non-dimensionalized governing equations associated with the boundary condition. Entropy creation in blood flow due to loss and magnetohydrodynamic processes is also investigated. Graphs and discussions of the effects of changing pertinent geometric and rheological factors on key flow characteristics, such as temperature, velocity, and mass concentration, are provided. Because of the small changes in blood temperature and mass concentration caused by the artery's curvature, it is observed that the radius of the curved channel has a significant impact on blood velocity. An increase in Brownian motion also resulted in a drop in the nano-temperature, a fluid's but the thermophoresis parameter exhibited the reverse behavior. [ABSTRACT FROM AUTHOR]

The arteriovenous fistula (AVF) is an essential vascular access for hemodialysis patients. AVF stenosis may occur at sites with abnormal wall shear stress (WSS) and oscillatory shear index (OSI), which are caused by the complex flow in the AVF. At present, an effective method for rapid determination of the WSS and OSI of the AVF is lacking. The objective of this study was to apply an ultrasound-based method for determination of the WSS and OSI to explore the risk sites of the AVF. In this study, the ultrasound vector flow imaging technique V Flow was applied to measure the WSS and OSI at four different regions of the AVF to detect and analyze the risk sites: (i) anastomosis region, (ii) curved region, (iii) proximal vein and (iv) distal vein. Twenty-one patients were included in this study. The relative residence time was calculated based on the measured WSS and OSI. The curved region had the lowest WSS; the anastomosis region had a significantly higher OSI (p < 0.05) compared with the venous regions, and the curved region had a significantly higher RRT (p < 0.05) compared with the proximal vein region. V Flow is a feasible tool for studying WSS variations in AVF. The possible risk site in the AVF may be located in the anastomosis and curved regions, where the latter could present a higher risk for AVF stenosis. [ABSTRACT FROM AUTHOR]

The current numerical investigation focuses on the sensitivity analysis of the pertinent parameters of the electrically conducting fluid (blood) with the suspension of Al 2 O 3 nanoparticles through the constricted arteries in the presence of stenosis, thrombosis and catheter. The mathematical model is developed to simulate the blood flow through the catheterized artery having irregular stenosis at the wall and thrombosis at the centre. The interactions of different physical phenomena like electroosmosis, radiation, Joule heating and a uniform radial magnetic field actuate the fluid flow. The nanoparticles shape effect is taken into account by considering the Crocine model. The governing equations are discretized by employing the Crank-Nicolson scheme, and the graphical portrayals for the impact of significant parameters on the flow characteristics have been devised and discussed. The statistical experiment is designed based on the parametric range of the parameter. The sensitivity analysis is performed on response surfaces after getting the best-fitted response surface relative to each response variable. The WSS profile negatively correlates with hematocrit parameter h m , Hartmann number M and positively related with Debye–Huckel parameter q e , while the reverse trend is observed for the impedance profile. The present work may be helpful in biomedical engineering, such as magnetic resonance angiography (MRA), which creates artery images. The integrated medical imaging and hemodynamic framework assist surgeons and researchers in better understanding the abnormalities caused by cardiovascular diseases and gaining a deeper grasp of the hemodynamic flow and other bodily fluids for surgical restoration. [ABSTRACT FROM AUTHOR]

• Benchmark solutions for dynamic analysis of complex rotor systems are derived. • The solutions are applicable to rotor systems with complicated geometries. • Benchmark solutions match well with FEM solutions. • It is convenient for analyzing the influence of arbitrary boundary condition. The rotor unbalance is a major source of rotor vibrations. Rotor vibrations often produce many undesired effects like noise, wear and fatigue, etc. In this paper, we try to seek the benchmark solutions for the unbalance responses of complex rotor-bearing system. The presented approach could be seen as the extension of transfer matrix method (TMM) in some sense. For the TMM, a disk or supporting structure cut off one uniform shaft element into two and someone must use the compatibility condition between these two new elements to derive the transitive matrix. However, for the presented approach, it directly solves the governing equations of uniform shaft elements with consideration of the effects of disks and supporting structures. Thus, this analytical approach is advantageous in reducing the times of matrix multiplication between state matrices and field matrices. One only needs to calculate the inversion of 16 × 16 dynamic stiffness matrix to find the steady state response. It saves the computer memory and is easy to be programmed. In addition, this analytical approach avoids the problems of selecting optimal discretization mesh densities in the case of FEM applications. For arbitrary linear boundary condition, the benchmark solutions are always easy to be obtained. The numerical simulation is carried out and two numerical examples are given to validate the new solutions. In which the finite element method is used as the numerical approach. Simulation results show that the benchmark solutions match very well with the FEM results. The effects of anisotropy in the supporting structures on the rotor's dynamic behavior, which are observed in this work, are also in accordance with many references. This validates the benchmark solutions further. [ABSTRACT FROM AUTHOR]

Heartbeat and respiration induce cyclic brain tissue deformations, which receive increasing attention as potential driving force for brain clearance. These deformations can now be assessed using a novel 3D strain tensor imaging (STI) method at 7 T MRI. An 18-year-old man had suffered a traumatic brain injury and was treated with a craniotomy with a maximal diameter of 12 cm. STI was employed to capture cardiac-induced brain tissue deformations and additional time-resolved 2D flow measurements were acquired to capture cerebrospinal fluid (CSF) flow towards the spinal canal. The craniotomy caused major changes in all aspects of the brain's mechanical dynamics as compared to healthy volunteer references. Tissue strains increased, particularly around the craniotomy, and directionality of deformations showed large abnormalities, also in the contralateral hemisphere. As the brain tissue could pulsate outward from the skull, physiological pulsatile CSF flow at the foramen magnum was abolished. This work illustrates how STI can assess physiological patterns of brain tissue deformation and how craniotomy leads to widespread deformation abnormalities that can be detected at a single patient level. While this case is meant to provide proof of concept, application of STI in other conditions of abnormal brain mechanical dynamics warrants further study. • Case study of craniotomy shows abnormal cardiac-induced brain deformations. • Brain deformations captured using novel 3D strain tensor imaging method at 7 T MRI. • Craniotomy causes major changes in brain dynamics, including the contralateral side. • Craniotomy invalidates the Monro-Kellie doctrine. [ABSTRACT FROM AUTHOR]

This research culminates the arterial blood flow analysis through distinct stenotic regions. Four different forms of stenotic regions are woven together in present study, i.e. triangular, trapezoidal, overlapping (w-shape) and composite formations. The four reviewed stenotic formations are first time considered in such numerical analysis. The considered problem is modeled for an elliptical cross-sectional artery by means of cartesian coordinate system. The governing coupled Partial differential equations are decoded numerically over this elliptical cross-section by using free source CFD software Open-FOAM. A precisely refined and proper mesh is generated for each arterial stenotic segment. A high magnitude of flow profile with some minor disruptions is observed near the origin of stenotic sections of artery. Pressure profile also has high values near the sharp corners of stenotic regions. Some expected irregularities in the flow profile are observed near the origin of stenotic regions as it happens in most of the real-life stenosed artery blood flow problems. [ABSTRACT FROM AUTHOR]

In this paper, a numerical investigation is carried out to study the blood flow behavior within the stenosis artery. An artery is under applying a constant heat flux on the boundary walls in this simulation. Lumen model is employed for simulation of the artery and the Sisko model is used to indicate properties of blood as non-Newtonian fluid. Also, the cone geometry of stenosis with different severities and radii are simulated. Then, effects of heat flux, different severities of stenosis, and different radii of the artery are studied on the blood flow behavior. It is reported that before stenosis, velocity is increasing and heat transfer rate is also increasing which cause temperature to be decreased in stenosis position. But after stenosis, velocity is decreased. Consequently, heat transfer rate is decreased which leads to reduction in blood temperature. Also, since the blood particles adhere to the arterial wall, with increasing radial distance from the walls, velocity is increased, which causes maximum velocity to be found in the central region. Moreover, the thermal driving force is damped in the lateral region of the artery and does not affect velocity. On the other side, as the severity increases step by step, the temperature decreases, respectively. In fact, the cross-sectional area decreases with increasing severity of stenosis. Consequently, velocity increases and causes heat transfer enhancement, which leads to a reduction in blood temperature. Therefore, the highest temperatures are related to the artery with an intensity of 20%. Although the cross-section area of the artery can change blood temperature, but its role can be ignorable in temperature enhancement and body healthy in this regard. [ABSTRACT FROM AUTHOR]

Decellularized porcine aortas are proposed as scaffolds for revolutionary active aortic grafts. A change in the static and dynamic mechanical properties, associated with the microstructure of elastin and collagen fibers, corresponds to alteration in the cyclic expansion and perfusion, in addition to possible graft damage. Therefore, the present study thoroughly investigates the mechanical response of the decellularized scaffolds of human and porcine origin to static and dynamic mechanical loads. The responses of the native human and porcine aortas are also compared; this is unavailable in the literature. Because the aorta is subjected to pulsatile blood pressure, dynamical responses to cyclic loads and their associated viscoelastic properties are particularly relevant for advanced graft design. In parallel, this study examines the microstructure of the decellularized aorta. The resulting data are compared to the analogous data obtained for the native human and porcine tissues. The results indicate that by using an optimized decellularization protocol – based on sodium dodecyl sulfate (SDS) and DNase – that minimizes mechanical and structural changes of the tissue, layered scaffolds with static and dynamic properties very similar to natural human aortas are obtained. In particular, a decellularized porcine aorta is non-inferior to a decellularized human aorta. About 55,000 patients undergo abdominal aortic aneurysm repair annually in the USA. The currently implanted grafts present a large mechanical mismatch with the native tissue. This increases the pulsatile nature of the blood flow with negative consequences to the organ perfusion. For this reason, biomimetic and mechanically compatible grafts for aortic repair are urgently needed and they can be obtained through tissue engineering. In this study, scaffolds from porcine and human aortas are obtained from an optimized decellularization protocol. They are accurately compared to the native tissue and present the ideal static and dynamic mechanical properties for developing innovative aortic grafts. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Investigate the transportation dynamics of pulsatile post-stenotic flows using a Lagrangian pathline extension technique. • Identify flow features relevant to the transport behaviours through path-dependent quantities. • Measure the percentage of remaining fluid and the depletion efficiency, analyzing their dependence on pulsatility. • Establish a criterion to evaluate the energy-saving transportation performance of post-stenotic flows. A comprehensive experimental study was performed to characterize the fluid transportation processes in pulsatile post-stenotic flows. This study aims to understand the effect of pulsatility on the transportation dynamics of post-stenotic flows and to establish a non-dimensional number to quantify transportation effectiveness in these flows. Two-dimensional particle tracking velocimetry measurements were conducted in a close flow loop with a symmetric stenosis model. A pathline extension algorithm is then applied to the obtained Lagrangian data, such that fluid parcels are continuously tracked as they flow through the region of interest. Pulsatile flows at Reynolds numbers Re m = 1000 , 2000 , 4000 , Strouhal number St = 0.05 , 0.1 , 0.15 and amplitude ratio λ = 0.4 and 0.8 are systematically investigated to understand the influence of pulsatility on the transport and mixing dynamics. The flow structures, such as the formation and evaluation of vortex rings, Kelvin-Helmoltz instabilities, jet meandering and breakdown, are clearly revealed by the lifespan parcel trajectories and the particle residence time (PRT). These structures are closely related to the transportation behaviours of the post-stenotic flows. Using the obtained Lagrangian results, the transportation effectiveness of the post-stenotic flows is further quantified by the depletion efficiency. The results demonstrate that while post-stenotic flows transport most residual fluids under a higher amplitude ratio, the depletion efficiency itself is insensitive to the amplitude ratio. The flow system operates more efficiently with high pulsatile frequencies (St = 0.8). Additionally, a transportation effectiveness parameter, Te , is defined to evaluate the transport performance by comparing the transportation efficiency to the pressure drop. The Te value is optimized at a high pulsatile frequency (St = 0.8) and a low amplitude ratio (λ = 0.4), with Te being up to twice as high as its counterpart in the steady flow. [ABSTRACT FROM AUTHOR]

• A low-cost, high-fidelity manufacture of a patient-specific compliant thoracic aorta. • Aortic flow measurements were carried out using the state-of-art Lagrangian particle tracking scheme – Shake-the-Box. • The velocity and wall shear stress at peak systole were in good agreement with in vivo MRI measurements. • The aortic distensibility and strain were estimated based on the flow measurements. • The relatively large lumen dimension change (42 %) in a cardiac cycle suggests the necessity of considering wall deformation in aortic flow studies. • Turbulent kinetic energy was calculated and visualized at peak systole. High-fidelity in vitro flow simulator in combination with high-dimensional flow visualization techniques can offer precise and comprehensive evaluation of aortic hemodynamics. However, it is particularly challenging to create a fully transparent aorta replica that faithfully mimics the aortic curvature and stiffness. In this study, we successfully manufactured a patient-specific compliant aorta phantom with a dilated ascending aorta that can be used in vitro hemodynamic study. We conducted pulsatile flow measurement on the deformable aorta replica using advanced 4D particle tracking velocimetry – Shake-the-Box. The aortic distensibility, circumferential strain, flow pattern, wall shear stress (WSS), and turbulent kinetic energy were assessed. Furthermore, the peak velocity field and WSS distribution were compared to in vivo MRI measurements. We found that the distensibility and circumferential strain of our aortic replica fell within the physiological range of young patients. The aortic diameter changed as much as 5.4 mm (42 %) in a cardiac cycle and the aortic distensibility was 9.9 × 10–3 mmHg-1. In addition, the obtained flow pattern and WSS distribution were found in a good agreement with in vivo MRI measurement. In conclusion, the compliant aorta phantom replicated the aortic wall material well. It also faithfully simulated the aortic flow and near-wall hemodynamics. The relatively large lumen dimension change (5.4 mm) in a cardiac cycle suggests the necessity of considering wall deformation in aortic flow simulations. We propose employing this approach for future studies, such as medical treatment training, validation of in silico fluid-structure interaction models, or as a complement to in vivo measurements. [ABSTRACT FROM AUTHOR]

Computational methodologies for predicting the fractional flow reserve (FFR) in coronary arteries with stenosis have gained significant attention due to their potential impact on healthcare outcomes. Coronary artery disease is a leading cause of mortality worldwide, prompting the need for accurate diagnostic and treatment approaches. The use of medical image-based anatomical vascular geometries in computational fluid dynamics (CFD) simulations to evaluate the hemodynamics has emerged as a promising tool in the medical field. This comprehensive review aims to explore the state-of-the-art computational methodologies focusing on the possible considerations. Key aspects include the rheology of blood, boundary conditions, fluid–structure interaction (FSI) between blood and the arterial wall, and multiscale modelling (MM) of stenosis. Through an in-depth analysis of the literature, the goal is to obtain an overview of the major achievements regarding non-invasive methods to compute FFR and to identify existing gaps and challenges that inform further advances in the field. This research has the major objective of improving the current diagnostic capabilities and enhancing patient care in the context of cardiovascular diseases. [ABSTRACT FROM AUTHOR]

Pulmonary capillary perfusion and gas exchange are physiological processes that take place at the alveolar level and that are fundamental to sustaining life. Present-day computational simulations of these phenomena are based on low-dimensional mathematical models solved in idealized alveolar geometries, where the chemical reactions between O 2 -CO 2 and hemoglobin are simplified. While providing general insights, current modeling efforts fail to capture the complex chemical reactions that take place in pulmonary capillary blood flow on arbitrary geometries and ignore the crucial impact of microstructural morphology on pulmonary function. Here, we propose a coupled continuum perfusion and gas exchange model that captures complex gas and hemoglobin dynamics in realistic geometries of alveolar tissue. To this end, we derive appropriate governing equations incorporating a two-way Hill-like relationship between gas partial pressures and hemoglobin saturations. We numerically solve the resulting boundary-value problem using a non-linear finite-element approach to simulate and validate velocity, partial pressure, and hemoglobin saturation fields in simple geometries. We further perform sensitivity studies to understand the impact of blood speed and acidity variability on key physiological fields. Notably, we simulate perfusion and gas exchange on anatomical alveolar domains constructed from 3D μ -computed-tomography images of murine lungs. Based on these models, we show that morphological variations decrease O 2 and CO 2 diffusing capacity, predicting trends and values that are consistent with current medical knowledge. We envision that our model will provide an effective in silico framework to study how exercise and pathological conditions affect perfusion dynamics and the overall gas exchange function of the respiratory system. Source code is available at https://github.com/comp-medicine-uc/alveolar-perfusion-transport-modeling. [ABSTRACT FROM AUTHOR]

Exploring the intricate interplay of heat transfer dynamics within two- and three-dimensional microchannels with static heat-spots, this study uncovers compelling insights into temperature distribution under varying wall conditions (adiabatic and constant wall temperature). The findings shed light on critical factors shaping heat transfer mechanisms. Key findings reveal that a channel with adiabatic walls experiences significantly higher temperatures than constant wall temperature cases, with a four-heat-spot configuration along the channel centerline yielding the highest temperatures. A stenosed channel experiences a larger temperature increase compared to the non-stenosed channel by a factor of 12–13 %. The study concludes with application to bio-fluid mechanics by studying hemodynamic condition in a bifurcated three-dimensional artery models. The location of heat-spots significantly influences the temperature distribution in the channel. A higher temperature rise appears in the case where heat-spot is located at the inlet of the narrower branch for the case of adiabatic wall conditions. These revelations hold promising implications for fields like medical science, where subtle temperature variations can indicate presence of inflammatory response in the blood vessel. [ABSTRACT FROM AUTHOR]

• Three inlets pulsatile water flow in hydroponic bed allowed the best lettuce yield. • Water temperature in 14.1–18.6 °C range reduced the harvesting period of lettuce. • Hydroponic system design by predicted fluid mechanics/heat transfer for waterflow. • CFD described water flow and water temperature in lettuce hydroponic bed. Experiments and computational modeling were developed to determine the effect of different types of hydraulic configurations on water quality variables to improve growth of lettuce in hydroponic beds. The variants in the hydraulic configurations consider water recirculation in hydroponic modules using Deep Water Culture technique (DWC), for continuous (CWF) and pulsatile water flow (PWF) using either one or three water flow inlets (TWF). These data were used to generate fluid mechanics and heat transfer models for the described hydraulic configurations to assess the effect of the hydraulic configuration on lettuce growth. The results obtained from the mathematical model by the finite volume method allowed to explain the influence of water flow and temperature on the rate of growing for lettuce during summer and autumn in the southern hemisphere. The main findings obtained from the hybrid numerical – experimental model to achieve high lettuce yield were that the number of water inlets has an effect on influenced nutrient transport and water quality variation, where the variant with three water inlets (TWF), and the climatic condition for autumn achieve better plant growth performance than summer. Computational modelling of fluid mechanics and heat transfer allowed to predict the variation of water quality variables in DWC bed, being a suitable technique with a high potential for achieving new accurate agriculture standards. [ABSTRACT FROM AUTHOR]

The formation of the stenosis in the carotid artery may lead to ischemic stroke, cerebral infarction, and other severe health-related complications. The present study aims to investigate the effects of heart rates on the blood flow dynamics and the heat transfer characteristics of a deformable stenosed carotid artery. This investigation employs an Arbitrary Lagrangian-Eulerian fluid-structure interaction based on the finite element-based solver COMSOL Multiphysics® to model the incompressible continuity, momentum, and energy equations. The model incorporates the elasticity of the carotid artery and the realistic non-Newtonian behavior of pulsatile blood flow. The effect of heart rates (75, 100, 120 bpm), degree of stenosis (25 %, 50 %, 75 %), arterial wall stiffness values (2–3 MPa), and macrophage heat generation (Q ̇ m = 0.05–0.2 W/mm3) have given insights into pulsatile blood flow dynamics and resultant alterations in thermal characteristics. As heart rates and degree of stenosis increase, the blood supply is severely affected in the internal carotid artery (ICA) connected to cerebral tissues, potentially increasing the risk of ischemic stroke due to inadequate oxygenation. Notably, recirculation zones or vortices form at 100 and 120 bpm heart rates, particularly at 75 % stenotic severity. Higher heart rates correspond to increased wall shear stress in the stenosed ICA region, potentially leading to endothelial damage and vessel rupture, posing significant health risks. At a heart rate of 75 bpm, the temperature increase in macrophages and plaques is 2.07 °C and 0.17 °C, respectively. It highlights the notable impact of heart rate and changes in stenotic severity on temperature distribution, particularly within macrophages in the presence of arterial plaque. These effects are more pronounced with lower heart rates, higher stenosis, and higher heat generation rates associated with arterial plaque. These findings suggest clinical relevance in understanding the complex interplay between heart rates, blood flow dynamics, and thermal characteristics in arterial stenosis scenarios. [ABSTRACT FROM AUTHOR]

Although the analysis of the flow enhancement of non-Newtonian fluids produced by pulsatile flows through tubes is common in the literature, the case of Carreau fluid has not been analyzed, which is the aim of this work. This study determines the flow enhancement caused by the pulsatile fluid flow through (a) a circular tube and (b) a concentric annular tube. We show that the flow rate enhancement of the shear-thinning fluid is controlled by the Carreau number C u , the Womersley number W o , the fluid power-law index n , the ratio between the outer and inner radii κ , a parameter β that represents the ratio between the infinite and zero-shear viscosities, and the amplitude of the oscillatory signal ɛ. In both cases (a) and (b) , a numerical solution of the start-up of the hydrodynamic is evaluated. With the aid of the velocity solution, the volumetric flow rate is determined under periodic conditions after the initial transient has vanished. Then, the fractional increase in the mean flow rate I due to the pulsatile pressure gradient is calculated. Furthermore, an asymptotic solution for small, intermediate, and very large values of the Carreau number is performed to provide physical insight into flow enhancement. • Flow enhancement of a shear-thinning fluid through cylindrical and concentric annular tubes is studied. • A pulsatile pressure gradient causes the flow. • The rheology of the fluid follows the Carreau model. • Particular values of the Carreau number exist where the flow enhancement is a maximum. • For small, intermediate, and very large values of the Carreau number, asymptotic and numerical results for the flow enhancement were derived. [ABSTRACT FROM AUTHOR]

To compare the accuracy of real-time phase-contrast echo-planar MRI (EPI-PC) and conventional cine phase-contrast MRI (Conv-PC) and to assess the influence of spatial resolutions (pixel size) and velocity encoding on flow measurements obtained with the two sequences. Flow quantification was assessed using a pulsatile flow phantom (diameter: 9.5 mm; mean flow rate: 1150 mm3/s; mean flow velocity: 1.6 cm/s). Firstly, the accuracy of the EPI-PC was checked by comparing it with the flow rate in the calibrated phantom and the pulsation index from Conv-PC. Secondly, flow data from the two sequences were compared quantitatively as a function of the pixel size and the velocity encoding. The mean percentage difference between the EPI-PC flow rate and calibrated phantom flow rate was −2.9 ± 2.1% (Mean ± SD). The pulsatility indices for EPI-PC and Conv-PC were respectively 0.64 and 0.59. In order to keep the flow rate measurement error within 10%, the ROI in Conv-PC had to contain at least 13 pixels, while the ROI in EPI-PC had to contain at least 9 pixels. Furthermore, Conv-PC had a higher velocity-to-noise ratio and could use a higher velocity encoding than EPI-PC (20 cm/s and 15 cm/s, respectively). The result of this in vitro study confirmed the accuracy of EPI-PC, and found that EPI-PC can adapt to lower spatial resolutions, but is more sensitive to velocity encoding than Conv-PC. [Display omitted] • Compared to conventional phase-contrast MRI (Conv-PC), echo-planar phase-contrast MRI (EPI-PC) can provide flow rate in real-time. • EPI-PC can accurately quantify flow rate and flow waveforms. • Compared to Conv-PC, EPI-PC can adapt to lower spatial resolution. • Excessive velocity encoding has a greater impact on the accuracy of EPI-PC compared to Conv-PC. [ABSTRACT FROM AUTHOR]

This paper reports perfusion culture of human umbilical vein endothelial cells (HUVECs) on a microporous membrane in a pressure-driven microphysiological system (PD-MPS), which we developed previously as a multi-throughput perfusion culture platform. We designed fluidic culture unit with microporous membrane to culture HUVECs under fluidic shear stress and constructed a perfusion culture model in the PD-MPS platform. Four fluidic culture units were arranged in the microplate-sized device, which enables four-throughput assay for characterization of HUVECs under flow. Medium flow was generated above and below the membrane by sequential pneumatic pressure to apply physiological shear stress to HUVECs. HUVECs exhibited aligned morphology to the direction of the flow with shear stress of 11.5–17.7 dyn/cm2 under the flow condition, while they randomly aligned under static culture condition in a 6 well plate. We also observed 3.3- and 5.0-fold increase in the expression levels of the thrombomodulin and endothelial nitric oxide synthase mRNAs, respectively, under the flow condition in the PD-MPS compared to the static culture in 6 well plate. We also observed actin filament aligned to the direction of flow in HUVECs cultured under the flow condition. [Display omitted] [ABSTRACT FROM AUTHOR]

Arterial stenosis poses a high cardiovascular risk, and clinical intervention is needed when these stenoses grow beyond a specific limit. The study of vortex dynamics in these diseased arteries can be beneficial to understand its severity. Therefore, in the present work, we have investigated the flow structures in an S-bend arterial geometry with different levels of stenosis using a sharp interface immersed boundary method. We have observed an onset of Kelvin-Helmholtz-type vortex roll-up for higher degrees of stenoses. Fluctuations in the wall shear stress are observed for higher stenosis degrees. However, these fluctuations depend on the position and length of the stenosis. Newtonian and non-Newtonian Carreau fluids predict similar vortex structures, although minor differences in the Kelvin-Helmholtz vortex structures and associated fluctuations are observed in the diastolic phase. The Newtonian fluid predicts a slightly longer low time-averaged wall shear stress (≤0.5 Pa) region immediately after the stenosis compared with the Carreau fluid in the 58 % blockage S-bend artery. [ABSTRACT FROM AUTHOR]

• Soluble HA levels are elevated in CAP and ARDS plasma and are associated with an increase in 28-day mortality. • Soluble HA levels correlate with disease severity and markers of inflammation, endothelial cell activation, and basement membrane destruction. • Small and large HA fragments are detected in plasma of most severe CAP or ARDS patients. • Pneumolysin induces HA release from human pulmonary microvascular endothelial cells. • Pneumolysin-induced HA shedding is dependent on reactive oxygen species production and is not associated with endothelial barrier dysfunction. Shedding of hyaluronan (HA), the component of endothelial cell (EC) glycocalyx, has been associated with acute lung injury. HA degradation allows plasma proteins and fluid to penetrate across the vascular wall leading to lung edema formation and leukocyte recruitment. Here, we analyzed sHA levels and size in patients with community-acquired pneumonia (CAP) and acute respiratory distress syndrome (ARDS), correlated them to disease severity, and evaluated the impact of pneumolysin (PLY), the Streptococcus pneumoniae (S.p.) exotoxin, on HA shedding from human pulmonary microvascular EC (HPMVEC). sHA levels were elevated in CAP and ARDS and correlated with the CRB65 severity score and with markers of inflammation (interleukin-6), EC activation (E-selectin), and basement membrane destruction (collagen IV). Furthermore, sHA levels were associated with an increase in 28-day mortality. Small and large sHA fragments were detected in plasma of most severe CAP or ARDS patients, and the presence of large sHA fragments was accompanied by the elevated levels of circulating collagen IV. In vitro, PLY induced sHA release from HPMVEC. This effect was dependent on reactive oxygen species (ROS) production and was not associated with endothelial barrier dysfunction. Conversely, HA shedding was impaired following HPMVEC infection with a S.p. PLY-deficient mutant. Our study identifies association between the severity of CAP and ARDS and the levels and size of sHA in plasma. It links sHA levels with, inflammation, EC activation status and basement membrane disassembly in ARDS and provides insights into the mechanism of HA shedding during infection. [ABSTRACT FROM AUTHOR]

• First study on nonlinear dynamic stability of buckled nanotube under pulsatile flow. • Develop the two-step perturbation- Galerkin truncation, R-K method and IHBM. • Reveal the local bifurcation mechanism at the stability boundary and global chaos. • Reveal the dual influences of structural size-dependence on local/global dynamics. • Hysteresis depends largely on whether chaos band covers the stability boundary. For bistable structures such as post-bucked nanotubes, the size-dependence may have influences on both local and global dynamics. A local/global dynamic instability study of post-buckled nanotubes transporting pulsatile flow is conducted for the first time. To model the size-dependence of both the solid and fluid, the nonlocal strain gradient beam model coupled with surface elasticity is established, and the slip-flow model is introduced. The governing equations are derived based on Zhang-Fu's refined beam theory and von Kármán type geometric relationship. A new computation mode is developed that combines the two-step perturbation- Galerkin truncation, incremental harmonic balance method (IHBM), and Runge-Kutta method to obtain the stability boundary and amplitude-frequency bifurcation diagram. Also, the dynamic characteristics in different parameter regions are presented through displacement-time history diagram, phase diagram, Poincaré map and spectrum diagram. The complex motions of local attractor- two-well chaos- global snap-through, and hysteresis are observed. Subsequently, the nonlinear dynamic instability mechanism and the physical significance of stability boundary are revealed. It is revealed that the structural size-dependence have dual effects and may change the bifurcation topology, such as the change of motion from local attractor to global attractor, and from periodic motion to chaotic motion. [ABSTRACT FROM AUTHOR]

• Formulation of the photo-gravitational planar elliptic restricted four body problems. • Determination of equilibrium points and their Floquet stability analysis under the influence of radiation pressure effect. • Numerical treatment of zero velocity curves under the influence of radiation pressure effect. • Estimation of Newton–Raphson basins of attraction associated to each attracter and analysis of radiation pressure effect. An important and pivot aspect of a dynamical system is the stability property and its range, which play a crucial role towards the stabilisation of a mission design. Present paper deals with Floquet stability analysis of equilibrium points and estimation of pulsating zero velocity curves and Newton–Raphson basins of attraction associated to these equilibrium points under the radiation pressure effect in the photo-gravitational planar elliptic restricted four body problem. Floquet stability test for the equilibrium points is performed with the help of the transition curves, which are generated under the influence of radiation pressure. It is noticed that stability range of the respective equilibrium points have deviated due to radiation pressure. To observe the possible regions of motion for restricted body, the pulsating zero velocity curves are numerically explored after establishing an invariant relation. It is found that not only the radiation parameter but also eccentricity and true anomaly reflect a considerable impact on the shape and size of forbidden regions. To see the tendency of randomly selected points in the phase space, Newton–Raphson basins of attraction associated to each attractor are estimated and effects of perturbing parameters are analysed. It is observed that effects of radiation and mass parameters are considerable however, that of eccentricity and true anomaly are negligible. Moreover, from probability distribution bar diagram, most probable number of iterations is 10 for the case when two primaries are of equal masses and third one is different, whereas it is 20 for the case when all primaries are of identical mass. These results will be helpful to study the generalised problem along with other kind of perturbations. [ABSTRACT FROM AUTHOR]

Endothelial cells (ECs) are the primary cellular constituent of blood vessels that are in direct contact with hemodynamic forces over their lifetime. Throughout the body, vessels experience different blood flow patterns and rates that alter vascular architecture and cellular behavior. Because of the complexities of studying blood flow in an intact organism, particularly during development, the field has increasingly relied on in vitro modeling of blood flow as a powerful technique for studying hemodynamic-dependent signaling mechanisms in ECs. While commercial flow systems that recirculate fluids exist, many commercially available pumps are peristaltic and best model pulsatile flow conditions. However, there are many important situations in which ECs experience laminar flow conditions in vivo, such as along long straight stretches of the vasculature. To understand EC function under these contexts, it is important to be able to reproducibly model laminar flow conditions in vitro. Here, we outline a method to reliably adapt commercially available peristaltic pumps to study laminar flow conditions. Our proof-of-concept study focuses on 2D models but could be further adapted to 3D environments to better model in vivo scenarios, such as organ development. Our studies make significant inroads into solving technical challenges associated with flow modeling and allow us to conduct functional studies toward understanding the mechanistic role of shear forces on vascular architecture, cellular behavior, and remodeling in diverse physiological contexts. [ABSTRACT FROM AUTHOR]

Equilibrium position, as well as dynamic patterns of suspended particles, plays a dominant role in particle manipulation of segregation, transporting, or sorting. The current paper aims to investigate the falling manners of non-circular particles in an enclosure while the pulsatile flow is involved as a counter-flow. The direct-forcing immersed boundary method is coupled with the lattice Boltzmann method to simulate this widespread issue numerically. Corresponding boundary conditions are hired to take into account pulsatile flow. Findings were first successfully verified against the existing literature and the accuracy of the results is well-demonstrated. For the first time, a series of proof-of-principal simulations with an increased level of geometric complexity, particle aspect ratio, as well as the number and initial configuration (release positions), is carried out. The force resulting from the particle acceleration is also considered. It is shown that considering such factors, particle settling manners would markedly differ. The collective behavior of particles is also studied, and it is revealed that the presence of neighboring particles makes the influence of the particle shape less clear; however, pulsatile flow presents considerable differences in the settling manners of particles. [ABSTRACT FROM AUTHOR]

To evaluate cerebrospinal fluid (CSF) flow dynamics and volume changes of pulsatile tinnitus (PT) patients induced by sigmoid sinus wall dehiscence (SSWD) with intracranial hypertension. Thirty-five SSWD-PT patients coexisted with intracranial hypertension and 35, age-, gender-, and handedness-matched healthy volunteers were prospectively enrolled and performed MRI. Clinical data were collected. CSF flow dynamics were evaluated by phase-contrast magnetic resonance imaging (PC-MRI) and CSF volume was measured using ITK-SNAP software. Compared with controls, the body mass index (BMI) of PT patients increased significantly (P = 0.046). Among CSF flow dynamics, PT patients presented significantly decreased mean flux (MF) (P = 0.017), mean velocity (MV) (P = 0.038), peak velocity (PV) (P = 0.023), and significantly increased regurgitant fraction (RF) (P = 0.010) than controls. There were no significant differences in other CSF flow dynamics parameters between the groups. CSF volume of PT patients was significantly increased than controls (P = 0.024). RF and CSF volume had potential diagnostic value. The AUC, sensitivity, specificity and accuracy of RF and CSF volume were 0.678, 68.6 %, 60.0 %, 61.4 % and 0.656, 68.6 %, 57.1 %, 55.7 %, respectively. The combined diagnostic efficacy of RF and CSF volume was highest, and the AUC, sensitivity, specificity and accuracy were 0.733, 74.3 %, 62.9 %, 67.1 % respectively. SSWD-PT patients present CSF flow dynamics and volume changes, which may be related to the occurrence of PT. In addition to structural abnormalities, the combination of RF and CSF volume can be innovative as a complementary index to identify SSWD as the accurate etiology of PT. [ABSTRACT FROM AUTHOR]

Although the hemodynamics of cerebral aneurysms have been extensively studied using patient-specific computational fluid dynamics techniques, no specific hemodynamic factors characteristic of cerebral aneurysm development have yet been identified. We believe that one problem with previous hemodynamic studies of cerebral aneurysms has been the manner in which control groups were created for comparison with experimental groups. The purpose of this study was to determine hemodynamic factors that correlated with the development of cerebral aneurysms. The control group was established in a manner that differed from those of previous works. This allowed us to demonstrate the effectiveness of our method. We artificially removed aneurysms in the middle cerebral artery bifurcations of nine patients and reconstructed the vessel geometries before the aneurysms had occurred. Pulsatile blood flow simulations were performed using the vessel geometries ipsilateral and contralateral to the sites of aneurysm removal, and hemodynamic metrics were calculated. Use of the ipsilateral and contralateral sides as the experimental and control sites, respectively, allowed us to evaluate statistically the hemodynamic metrics between the two corresponding sites/groups. The results showed that only the normalized transverse wall shear stress (NtransWSS) was significantly higher at the MCA bifurcation ipsilateral to the site of aneurysm removal than at the contralateral bifurcation (p = 0.01). There were no significant differences in the other hemodynamic metrics between the bilateral bifurcations. Our findings imply that multi-directional disturbed wall shear stress, which is detected by the NtransWSS metric, may be one hemodynamic risk factor for the development of cerebral aneurysms. [ABSTRACT FROM AUTHOR]

Microcirculation of blood and transport of oxygen play important roles in the biological function of the optic nerve and its diseases. This work develops a multi-domain model for the optic nerve, that includes important biological structures and various physical mechanisms in blood flow and oxygen delivery. The two vascular networks are treated as five domains in the same geometric region, with various exchanges among them (such as Darcy's law for fluid flow) and with the tissue domain (such as water leak, diffusion). The numerical results of the coupled model for a uniform case of vasculature distribution show mechanisms and scales consistent with literature and intuition. The effects of various important model parameters (relevant to pathological conditions) are investigated to provide insights into the possible implications. The vasculature distribution (resting volume fractions here) has significant impacts on the blood circulation and could lead to insufficient blood supply in certain local regions and thereby affect the delivery of oxygen. The water leak across the capillary wall will have nontrivial effects after the leak coefficients pass a threshold. The pulsatile arterial pressure leads to expected pulsatile patterns and stable spatial profiles, and the uniform case is almost the averaged version of pulsatile case. The effects of viscosity, the stiffness of blood vessel wall, oxygen demand, etc. have also been analyzed. The framework can be extended to include ionic transport or to study the retina when more biological structural information is available. • A multi-domain model with vasculature is developed for optic nerve microcirculation. • The model includes various physical mechanisms for blood flow and oxygen transport. • The vasculature distribution has significant impact on local blood and oxygen supply. • Pulsatile arterial pressure produces similar averaged quantity as constant pressure. • Effects of the leak across blood vessel wall and other parameters are investigated. [ABSTRACT FROM AUTHOR]

This study aimed to optimize parameters for cultivating adipose-derived stem cells (ADSCs) in hollow fiber membrane systems. Enhanced ADSC cultivation was achieved in this study by utilizing a higher cell seeding rate (10 mL/min) and fibronectin coating (8 μg/cm²) on the membrane. A pulsatile flow perfusion (30 min on / 3 h off) for 24 h, followed by continuous flow perfusion at a lower rate (<20 mL/min), was employed. Notably, a two-day medium change maintained CD73 expression (79.26 %) compared to scenarios without changes (1.92 %) over eight days. Using a membrane cut-off of 20 kDa and <0.1 μm, a 1.4- and 2.8-fold increase in proliferated cells was observed; however, CD73 expression decreased by 10.07 and 33.63 %, respectively. The membrane with a pore size of <0.1 μm exhibited 1.4-fold higher exosome particle numbers. In conclusion, nutrient supplementation emerged as crucial for optimal ADSC cultivation in hollow fiber systems. [Display omitted] • This study aimed to optimize parameters for cultivating adipose-derived stem cells (ADSCs) in hollow fiber membrane systems. • Investigated hollow fiber feasibility for stem cell cultivation and exosome production. • Two-day medium change increased cell proliferation by 3 times. • Stemness marker increases 3x on <0.1 µm MWCO fiber membrane vs. 20 kDa membrane. • Proved nutrient supply significantly influences stemness, proliferation, and exosome production. [ABSTRACT FROM AUTHOR]

The hemodynamic assessment of patients with left ventricular assist devices (LVAD) using noninvasive blood pressure (NIBP) monitoring may be unreliable without pulsatile blood flow. The primary goal of this study is to examine the association between intraoperative blood pressure monitoring gaps of 10 min or greater and LVAD type in patients undergoing noncardiac surgeries with NIBP monitors at induction. Retrospective cohort. Single institution, academic university hospital. One-hundred fifteen patients undergoing 187 noncardiac surgeries without arterial lines at induction. Noncardiac surgery. The primary outcome was the association of blood pressure monitoring gaps, which were defined as ten minutes or greater, and LVAD type including the HeartMate 2 (HM2; Abbott, Chicago, IL) and the HeartMate 3 (HM3; Abbott, Chicago, IL), as evaluated by multivariable logistic regression analysis. After adjusting for patient characteristics, HM3 was associated with lower odds of monitoring gaps (p = 0.02). Additionally, the odds of a monitoring gap were higher in patients with morbid obesity (p = 0.04) and in surgical duration longer than 180 min (p = 0.001). In the post-hoc analysis, morbid obesity, general anesthesia, and prolonged surgeries were found to be associated with increased odds of arterial line placement after induction (p = 0.05, p = 0.007, p < 0.001). Patients with a HM2 undergoing noncardiac surgery had nearly three-fold higher odds of blood pressure monitoring gaps of 10 min or greater compared to patients with a HM3. Morbid obesity and prolonged surgical duration were also associated with a significant increase in monitoring gaps. Morbid obesity, general anesthesia, and longer surgical duration were found to have a greater odds of arterial line placement after induction. These results may help anesthesiologists determine the appropriateness of NIBP in patients with LVADs undergoing noncardiac surgeries. [Display omitted] • During noncardiac surgeries, the HM2 LVAD had higher odds of BP monitoring gaps. • LVAD patients had higher odds of BP gaps with morbid obesity and longer surgery. • Consider NIBP alternatives when factors with higher odds of BP gaps are present. [ABSTRACT FROM AUTHOR]

This paper explores the application of Physical-informed Neural Networks (PINNs) for reconstructing ship propeller wake fields, introducing a novel approach known as self-adaptive loss balanced physics-informed neural networks (LB-PINNs). It can enhance the accuracy of the reconstruction process by incorporating an adaptive weight to balance the loss term within the network. The initial sections of the paper present the foundational principles and framework of PINNs. To validate the efficacy of PINNs in solving partial differential equations, the well-known Burgers equation is applied and then these results with those obtained through LB-PINNs are compared. This comparative analysis highlights the superior performance of LB-PINNs in achieving accurate predictions. Moving forward, the open water characteristics of the KVLCC2 propeller are simulated by using computational fluid dynamics (CFD) software STAR CCM+, and the flow field information of the KVLCC2 propeller in open water is obtained. This simulation provides crucial flow field information, forming the basis for constructing a training sample set to train the neural network. The trained PINN and LB-PINN are used to infer approximate solutions of the governing equations at arbitrary time and space coordinates. The velocity and pressure distributions obtained by PINN and LB-PINN were compared with those simulated by STAR CCM+. The results confirm the applicability of both PINN and LB-PINN in the reconstruction of propeller wake fields, with LB-PINN demonstrating superior performance. • A novel method for solving governing differential equations of fluid mechanics based on LB-PINN is introduced. • LB-PINN's adaptive weight balances the loss term, reducing mean square error by an order of magnitude compared to PINN. • Sparse numerical simulation data suffices for LB-PINN training, enabling ship propeller wake reconstruction. • Comparing flow field reconstructions using PINN, LB-PINN, and CFD shows LB-PINN's validity and accuracy. [ABSTRACT FROM AUTHOR]

[Display omitted] Recognizing the significance of drug carriers in the treatment of atherosclerotic plaque is crucial in light of the worldwide repercussions of ischemic stroke. Conservative methodologies, specifically targeted drug delivery, present encouraging substitutes that mitigate the hazards linked to invasive procedures. With the intention of illuminating their considerable significance and prospective benefits, this study examines the impact of the geometry and dimensions of drug-loaded nano-microcarriers on atherosclerotic plaque. The research utilizes a finite element approach to simulate the motion and fluid dynamics of nano-microcarriers loaded with drugs within the carotid arteries. Carriers are available in a variety of shapes and sizes to accommodate patient-specific geometries, pulsatile fluid flow, and non-Newtonian blood properties. Optimization of drug delivery is achieved through the examination of carrier interaction with the inner wall. The results demonstrated that the interaction data between particles and the inner wall of atherosclerotic plaques exhibits micro- and nanoscale patterns that are distinct. Symmetric plaques demonstrate that nanoparticles with a 0.4 shape factor and diameters below 200 nm show the highest interaction rate. Conversely, larger particles (200 and 500 nm) with shape factors of 1 demonstrate comparatively elevated interaction rates. The optimal shape factor for drug-loaded microparticles has been determined to be one, and the number of interactions increases as the diameter of the nanoparticles increases, with a significant increase observed at a shape factor of one. Asymmetric plaques exhibit the maximum interaction rates among particles that have a shape factor of 0.4 and have diameters smaller than 500 µm. The findings establish a foundation for novel therapeutic strategies, establishing nano-microparticles as auspicious contenders for accurate and efficacious drug delivery systems that inhibit plaque proliferation. [ABSTRACT FROM AUTHOR]

The apparent viscosity of concentrated clay dispersions is a key control parameter in the ceramic industry, particularly in the manufacture of sanitaryware. Slips, the final industrial dispersions, are complex in their rheological behavior, featuring non-Newtonian flow and thixotropy. In this work, a resonance vibrating-rod viscometer (VRV) was utilized to evaluate the viscosity evolution over time, showing advantages over a classical rotational viscometer. Notably, while both viscometers were sensitive to small quantities of a deflocculant, the VRV effectively described the typical increase in the viscosity of clay dispersions at rest (thixotropy), the experimental data being properly fitted by a phenomenological model. As a relevant technical aspect, the superior suitability of the VRV for in-line process control was highlighted in the continuous monitoring of stirred clay dispersions and slip casting in plaster moulds. Additionally, a fitting model was developed to elucidate viscosity evolution during the casting process. In summary, this study underscores the versatility of the VRV as a control instrument in the sanitaryware industry. • The vibrating-rod viscometer (VRV) monitors sanitaryware clay dispersions. • Thixotropy characterization differs from classical rotational viscometers. • It provides a rapid response in stirred suspensions and slip casting. • Phenomenological models are applied for understanding viscosity data. • The VRV can function as a process control device in the ceramic industry. [ABSTRACT FROM AUTHOR]

• We firstly present two kinds of methods for the photonic hook generation by a dielectric micro-cylinder illuminated under an electric dipole using the finite element method. • A point dipole source, placed near the surface of the cylinder the propagation directions of the wave fronts illuminating the surface of the mesoscale dielectric cylinder are not parallel to each other, in contrast to classical plane-wave illumination. • Through changing the position and orientation of the point dipole, which can be considered as additional degrees of freedom to control the characteristics of the photonic hook, one can obtain the asymmetric illumination to produce the photonic hook. In this paper, we numerically investigate a photonic hook (PH) generated by a dielectric micro-cylinder illuminated under an electric dipole using the finite element method. At first, we show the properties of the photonic nanojet (PNJ) produced by the micro-cylinder under an electric dipole. Then, we find that a PH can be obtained when the electric dipole is moved at a certain distance along the direction perpendicular to the center line of the cylinder. Considering the rotation symmetry of the model, we firstly present that a PH can be generated by changing the orientation of the electric dipole. And the power flow of the PHs produced by different orientated dipoles are studied. Finally, the PHs properties affected by the gap distance between the micro-cylinder and the electric dipole and the refractive index of the micro-cylinder are investigated. Our results provide a method to generate a PH under a dipole illumination. And it may have potential applications in the quantum dot detection and microsphere super-resolution. [ABSTRACT FROM AUTHOR]

In the two-dimensional heat transfer experiments of aero-engine rotating disk cavities, the inverse heat transfer problem method can be used to obtain the wall heat flux numerically, which uses the two-dimensional measured wall temperature to solve the rotating disk heat conduction equation. A back propagation (BP) neural network data approximation method is proposed to reduce the ill-posedness of the two-dimensional inverse heat transfer problems in rotating disk cavities in this paper. The priori knowledge of wall temperature characteristics expressed by two-dimensional wall temperature first-order radial partial derivative distribution is used for BP neural networks' regularization. The distribution characteristics of the wall temperature first-order radial partial derivative in a typical preswirl rotating disk cavity were investigated by the flow-thermal coupling numerical simulation. Based on these characteristics, the BP neural network construction and training method with uncertain regularization coefficient is adopted. The numerical experiment results show that compared with the traditional polynomial fitting methods, the BP neural network approximation methods in this paper show significant advantages in data processing performance and stability; The fluctuation amplitude of the wall heat flux relative error on the disk surface can be reduced by 1–3 orders of magnitude, reducing the relative error of wall heat flux in most areas of the disk to within 20 % of the original value; The maximum wall heat flux relative error suppression area where | δq r ,cal / δq r ,mea × 100 %| < 100 % of BP neural network approximation method can reach 1.93 times that of the traditional fitting method, and 3.18 times for the area where | δq r ,cal / δq r ,mea × 100 %| < 30 % in the current study. • Wall temperature first-order radial partial derivative priori knowledge is used for BP neural network regularization. • The construction and training method of BP neural network with uncertain regularization coefficient is proposed. • The two-dimensional heat flux relative error fluctuation amplitude can be reduced by 1–3 orders of magnitude. • BP neural network shows significant advantages in data processing effect and stability compared with polynomial fitting. [ABSTRACT FROM AUTHOR]

The present study aims to investigate the fully developed electroosmotic flow of Carreau–Newtonian fluids within a circular tube, considering two different boundary conditions of zeta potential. The unsteady behavior of Carreau–Newtonian fluids, is attributed to the pulsatile pressure-driven flow. Studying two distinct formulations, slip and no-slip zeta potentials, illustrates the relative movement of fluid particles and the charged surface. The proposed study's framework is divided into two regions: a central region containing a non-Newtonian Carreau fluid exhibiting both shear-thinning and thickening behavior, and a peripheral region containing a Newtonian fluid with the effect of an electrical double layer at the solid wall of the cylindrical tube. The Poisson–Boltzmann equation under the assumption of Debye–Hückel approximation governs the potential distribution due to the electric double layer, facilitating the examination of electroosmotic flow through tube. Obtaining analytical solutions for the momentum equations in both regions becomes challenging due to the inclusion of pulsatile pressure-driven flow and a non-Newtonian Carreau fluid. Asymptotic series expansions are employed, utilizing small parameters such as the Weissenberg number (W e ≪ 1) and a pulsatile Reynolds number (α ≪ 1), to derive velocity expressions for both regions. Wall shear stress fluctuations, as indicated by time-averaged wall shear stress and oscillatory shear index are assessed to gauge the temporal variation of wall shear stress from the dominant blood flow direction. By utilizing potential and hydrodynamic variables, an asymptotic formulation for the streaming potential is developed to ascertain the asymptotic expression of electrokinetic energy conversion efficiency and scrutinize the impacts of pertinent physical parameters on it. The proposed study prominently shows that the Debye–Hückel parameter, Weissenberg number, pulsatile Reynolds number, and time-dependent pressure gradient significantly influence the fluid velocity, flow rate, and flow resistance. The notable determination of the present study is that the velocity amplitude and electrokinetic energy conversion efficiency are enlarged in the slip-dependent case relative to the no-slip zeta potential. It is noteworthy that as inertial forces become more prominent compared to viscous forces, both time-average wall shear stress and oscillatory shear index experience a slight decrease, although the reduction in oscillatory shear index is minimal owing to the absence of obstruction within the tube wall. The NDSolve numerical scheme in Mathematica software is employed to calculate numerical solutions for the governing equations, which are subsequently verified against results obtained through asymptotic analysis. The findings of this study are expected to deepen our understanding of unsteady electroosmotic flows of Carreau fluid and contribute to the design and development of advanced microfluidic devices with enhanced performance for various applications. [Display omitted] • Electroosmotic flow of Carreau–Newtonian fluids in a Circular tube is discussed. • Perturbation method is used for solution in terms of the small parameters (We, α). • An analytical expression for the streaming potential and EKEC is derived. • Slip-dependent formulation enlarged the amplitude of fluid velocity. • The study aims to design microfluidic devices for mixing and separation process. [ABSTRACT FROM AUTHOR]