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Active control methods are commonly employed in droplet-based microfluidics. While passive methods of droplet generation face limitations, active methods, including flow rate pulsations provide an avenue for precise control. We investigate the influence of sinusoidal pulsations of dispersed phase flow rate on the plug flow dynamics in a T-junction microchannel. The study covers a range of fluid sets, including gas-liquid and liquid-liquid systems. In the absence of pulsations, distinct regimes of plug formation were identified, and plug length, velocity, and natural frequency of formation were determined. Introducing flow rate pulsations at frequencies proportional to the natural ones f = fpulse/fplug, we observed distinct plug length distributions, including double- or triple-mode, drop-on-demand mode, and multi-mode distribution. The influence of pulsations on plug length was particularly notable at low dimensionless frequencies (f < 1), especially for fluid combinations with higher viscosity ratios. The model was proposed to explain plug length distribution patterns under pulsatile conditions. Micro-PIV measurements provided insights into the velocity fields within plugs, revealing the stretching of streamlines without altering plug length. Our findings contribute to the understanding of active control methods in droplet-based microfluidics and suggest potential applications for precise control over microfluidic processes.

Objective: The objective of this retrospective review was to evaluate whether or not pulsatile flow improves cerebral hemodynamics and clinical outcomes in pediatric congenital cardiac surgery patients. Methods: This retrospective study included 284 pediatric patients undergoing congenital cardiac surgery with cardiopulmonary bypass support utilizing nonpulsatile (n = 152) or pulsatile (n = 132) flow. Intraoperative cerebral gaseous microemboli counts, pulsatility index, and mean blood flow velocity at the right middle cerebral artery were assessed using transcranial Doppler ultrasound. Clinical outcomes were compared between groups. Results: Patient demographics and cardiopulmonary bypass characteristics between groups were similar. Although the pulsatility index during aortic crossclamping was consistently higher in the pulsatile group (P

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.

Background: With the increasing use of mechanical circulatory support for long-term augmentation of cardiopulmonary function, the need for safer devices is apparent. Pump thrombosis and failure, inadequate ventricular unloading, progressive right-sided dysfunction, and end-organ hypoperfusion are seen with long-term mechanical circulatory support devices. Generation of pulsatile flow has been proposed to mitigate some of these risks by providing physiologic flow and pressure profiles to the vascular system and end-organs. Modification of continuous flow devices to provide pulsatility may prove a cheap and effective way to achieve physiologic flow; however, effective use of such a technique has yet to be demonstrated. This work aims to describe these efforts, as well as mechanical arguments regarding the challenges to be overcome in achieving this goal. Methods: Prior literature and textbooks were used to develop the theoretical basis for the paper. Results: Attempts at generating pulsatile flow with continuous flow devices have been marred by difficulty in mitigating viscous effects on oscillating mechanical systems. Currently available devices and research setups have been unable to generate truly physiologic pulsatile flow systems. New devices are needed that utilize various forms of positive displacement in order to generate true pulsatile flow that mimic native waveforms generated by the heart. Conclusions: The mechanical challenges in generating pulsatile flow with continuous flow devices have precluded their widespread adoption in clinical practice. New pulsatile pumps are needed to achieve adequate physiologic pulsatility with improved side-effect profile.

The recent decline in RAAA incidence and the fast paced scenario with associated challenges regarding training calls for initiative for a better training environment to maximize learning. This led us to the creation of a pulsatile human cadaveric RAAA model. Fresh frozen cadaver was used to create RAAA with BioTissue in hybrid suite with ability to perform CBCTA for sizing. As a proof of concept, the model was used to perform REVAR with proximal CODA balloon control. The model proved to be feasible and we believe it is a better environment to train and gain adequate proficiency in RAAA management.

Herein, we present a case of aortic dissection with right carotid artery occlusion that was treated successfully with thrombus evacuation from the false lumen of the occluded carotid artery during hemiarch replacement. This procedure is performed with two maneuvers: aggressive retrieval of the thrombus from the innominate artery during circulatory arrest and thrombus evacuation from the false lumen of the right common carotid artery through a right neck incision with the heart beating. In this alternative method, thrombi can be evacuated more naturally and briskly, using pulsatile flow.

Atherosclerotic with the high occurrence of plaque formation due to stenosis has attracted wide attention among researchers. The left coronary artery has been studied in two-dimensional and in three-dimensional (3D) bifurcation as the models of blood flow through Newtonian and non-Newtonian fluids to better understand the physical mechanism. The computational Fluid Dynamics (CFD) technique is incorporated in COMSOL Multiphysics and then it is justified by satisfactory validation. It is found that the Newtonian model shows larger recirculation zones than non-Newtonian does. The present study also focuses on the evaluations of the lesion of diagnostic and the coefficient of pressure drop assessments on the basis of the diagnostic parameter’s critical values affected by the rheological model. Nevertheless, the leading concentration of the subsisting investigation works is confined to the change of importance factor (IFc) affected by arterial blockage. But the IFc of non-Newtonian fluid for 3D left coronary artery bifurcation model decreases with increasing bifurcation angle and the time-averaged inlet pressure is the least for smaller bifurcation angles. The current research further concentrates that the flow separation length reduces with developing bifurcation angle in bifurcated geometry. It is significant to mention that non-Newtonian blood flow model incorporating hemodynamic and diagnostic parameters has great impacts on instantaneous flow systems.

The current research deals with the MHD pulsating flow of two immiscible liquid layers with joule heating and first-order chemical reaction. The channel is partitioned into two regions with different fluid widths. The governing flow equations are transformed using a perturbation approach into a system of ODEs. The R-K 4th-order approach is used with the shooting technique to solve the resulting ODEs. The effect of several emerging parameters on flow characteristics is depicted graphically and explained. The impact of liquid widths on velocity distribution, temperature and concentration are also presented for the cases: (i) when kerosene dominates the fluid flow, (ii) when water dominates the fluid flow, (iii) when both fluids occupy equal space in the channel. Moreover, the Nusselt and Sherwood numbers are calculated at the boundaries of the channel and presented through 3-D graphs. Further, shear stress for both channel walls and mass flux results are presented in tabular form. The outcome predicts that stress at the lower boundary is always greater than at the upper boundary. And, when the rate of heat transfer is measured over time, it has an oscillatory nature and is higher at the lower boundary than at the upper boundary.

Extracorporeal membrane oxygenator is a life-saving critical medical equipment for cardio-pulmonary support, for treatment of severe chronic respiratory distress. The equipment performance is dependent on the type of membrane, flow configuration, and blood physiology. Lot of research efforts are focused on the development of novel membrane. However, the cardiovascular pulsations and blood physiological conditions on the flow and associated transport is important, which was not explored significantly. Here, we investigate the impact of the frequency of flow oscillations on the oxygenation profile. The physiological parameters which affect the blood oxygenation profile is investigated in detail. The oscillations in the oxygen transfer rate profiles are suppressed, as the blood flow rate is reduced, and the oxygen saturation is completely out-of-phase with the flow rhythm (saturation is maximum when the flow is minimum). We present the phase space to easily decide on the required combination of process variables or design specifications, needed to achieve the target oxygen saturation, based on the patient blood physiology. The present effort in understanding the process, can lead to improved performance and design of this life-supporting equipment. The results provide clear recommendations from the clinical perspectives. The outcome of the work will be useful to the engineering (biomedical) community in realizing the role of fluid flow and transport phenomena in extracorporeal oxygenation, under varied physiological conditions.

Objective: Identify risk factors for development of preeclampsia refractory to aspirin prophylaxis in women at high-risk of preeclampsia., Material and Methods: A retrospective cohort study analyzed 206 women identified as high-risk for preeclampsia through first-trimester screening and prescribed aspirin prophylaxis. We compared maternal characteristics, medical history, biochemical markers, and uterine artery Doppler indices between those with and without preeclampsia., Results: Women with preeclampsia had significantly higher rates of chronic hypertension (54.3% vs. 8.2%), higher first-trimester mean arterial pressure (MAP, 109.6 vs. 95.4 mmHg), and higher body mass index (BMI, 27.6 vs. 24.9) compared to controls. Second-trimester MAP and mean uterine artery pulsatility index (UtA-PI) were also significantly elevated in the preeclampsia group (103.3 mmHg and 1.39, respectively) compared to controls (89.7 mmHg and 1.05). ROC curve analysis identified an optimal second trimester UtA-PI cut-off of 1.36 for predicting preeclampsia, with sensitivity of 49% and specificity of 87.1%. When using a cut-off value of 0.77 for the second-to-first trimester UtA-PI ratio, the sensitivity and specificity were 60% and 90.6%, respectively., Conclusion: Chronic hypertension, high first and second trimester MAP, higher BMI, and elevated second trimester UtA-PI are associated with preeclampsia despite aspirin prophylaxis. Evaluating second trimester UtA-PI or the ratio of second to first trimester UtA-PI may be a promising tool for identifying women who do not respond to aspirin., Competing Interests: Conflict of interest The authors declare no conflict of interest., (Copyright © 2024. Published by Elsevier B.V.)

Background: First-trimester screening for preeclampsia using a combination of maternal risk factors and mean arterial pressure, uterine artery pulsatility index, and placental growth factor, as proposed by the Fetal Medicine Foundation, provides effective prediction of preterm preeclampsia. Placental dysfunction is a potential precursor of spontaneous birth., Objective: The objective of this study was to examine if the estimated risk of preeclampsia is associated with the gestational age at onset of spontaneous delivery in the absence of preeclampsia., Study Design: This was a secondary analysis of the data from the Screening programme for pre-eclampsia trial in which there was a comparison of the performance of first-trimester screening for preterm preeclampsia using the Fetal Medicine Foundation model vs a traditional history-based risk scoring system. A subgroup of women from the trial with spontaneous onset of delivery (labor with intact membranes or preterm prelabor rupture of membranes) was included in this study and was arbitrarily divided into 3 groups according to the risk for preterm preeclampsia as determined by the Fetal Medicine Foundation model at 11 to 13 weeks' gestation as follows: group 1 low risk (˂1/100); group 2 intermediate risk (1/50 to 1/100); and group 3 high risk (˃1/50). A survival analysis was carried out using a Kaplan-Meier estimator and a Cox regression analysis with stratification by the 3 preeclampsia risk groups. Occurrence of spontaneous birth in the study groups was compared using log-rank tests and hazard ratios., Results: The study population comprised 10,820 cases with delivery after spontaneous onset of labor among the 16,451 cases who participated in the Screening programme for pre-eclampsia trial. There were 9795 cases in group 1, 583 in group 2, and 442 in group 3. The gestational age at delivery was <28, <32, <35, <37, and <40 weeks in 0.29%, 0.64%, 1.68%, 4.52%, and 44.97% of cases, respectively, in group 1; 0.69%, 1.71%, 3.26%, 7.72%, and 55.23% of cases, respectively, in group 2; and 0.45%, 1.81%, 5.66%, 13.80%, and 63.12% of cases, respectively, in group 3. The curve profile of gestational age at spontaneous birth in the 3 study groups was significantly different overall and in pairwise comparisons (P values <.001). The Cox regression analysis showed that risks increased for spontaneous birth by 18% when the intermediate-risk group was compared with the low-risk group (P˂.001) and by 41% when the high-risk group was compared with the low-risk group (P˂.001)., Conclusion: In this study that investigated birth after spontaneous onset of labor in women without preeclampsia, there were 2 major findings. First, the duration of pregnancy decreased with increasing first-trimester risk for preeclampsia. Second, in the high-risk group, when compared with the low-risk group, the risk for spontaneous birth was 4 times higher at a gestational age of 24 to 26 weeks, 3 times higher at 28 to 32 weeks, and 2 times higher at 34 to 39 weeks. These differences present major clinical implications for antepartum counselling, monitoring, and interventions in these pregnancies., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Objectives: To examine the role of the cerebro-placental-uterine ratio (CPUR) in predicting composite adverse perinatal outcomes (CAPO) in patients with pregnancy-induced hypertension (PIH)., Study Design: This prospective, case-control study was conducted at a tertiary hospital with 110 cases of PIH, including 70 patients with preeclampsia and 40 with gestational hypertension, and 110 healthy controls. The middle cerebral artery pulsatility index (MCA-PI), umbilical artery pulsatility index (UA-PI), and uterine artery pulsatility index (UtA-PI) were measured, and the cerebro-placental ratio (CPR=MCA-PI/UA-PI) and CPUR (CPR/UtA-PI) were calculated., Main Outcome Measure: The role of CPUR in predicting CAPO in preeclampsia and gestational hypertension., Results: The CPR and CPUR values were lower in the PIH group compared to the control group (p < 0.001). CAPO had a negative correlation with CPR and CPUR (p < 0.001). Univariate regression analysis revealed that the likelihood of CAPO was increased four times by a low CPR value and six times by a low CPUR value. In the ROC analysis, the optimal cut-off value of CPR in predicting CAPO was 1.33 with 74 % sensitivity and 66 % specificity (area under the curve [AUC] = 0.778; p < 0.001) in PIH. For CPUR, the optimal cut-off value was 1.32, at which 82 % sensitivity and 79 % specificity in predicting CAPO (AUC=0.826; p < 0.001)., Conclusion: CPUR was determined to be successful with high sensitivity in predicting adverse perinatal outcomes in the presence of PIH. In addition, CPUR was more effective in predicting CAPO in patients with preeclampsia compared to gestational hypertension. CPUR can be used to predict adverse outcomes in patients with PIH., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 International Society for the Study of Hypertension in Pregnancy. Published by Elsevier B.V. All rights reserved.)

The idea of using magnetic field for therapeutic reasons is almost as old as the discovery of magnetism. The application of magnetic field in Biomechanics has become a significant field of research recently. Blood is a biomagnetic fluid and its flow in a cardiovascular system is likely to be affected by the application of an external magnetic field. Present numerical investigation deals with the magnetohydrodynamic flow of blood through a stenosed artery. Non-Newtonian behaviour of streaming blood is characterized by the Carreau viscosity model. Vessel wall flexibility is taken into account. Pulsatile flow of blood is governed by the Navier-Stokes equations along with the mass conservation equation. A finite difference scheme is developed and suitable initial and boundary conditions are imposed to solve these non-linear equations. Distributions of several significant hemodynamic wall parameters, such as wall shear stress, oscillatory shear index, etc. are examined over the entire flow regime with the variations of stenosis height and Hartmann number. Comparison with the Newtonian fluid for these wall parameters are also done. It is found that severe health complications may happen with the advancement of the disease.

Background: Assessing the umbilical artery pulsatility index via Doppler measurements plays a crucial role in evaluating fetal growth impairment., Objective: This study aimed to investigate perinatal outcomes associated with discordant pulsatility indices of umbilical arteries in fetuses with growth restriction., Study Design: In this retrospective cohort study, all singleton pregnancies were included if their estimated fetal weight and/or abdominal circumference fell below the 10th percentile for gestational age (2017-2022). Eligible cases included singleton pregnancies with concurrent sampling of both umbilical arteries within 14 days of birth at the ultrasound evaluation closest to delivery. The exclusion criteria included births before 22 weeks of gestation, evidence of absent or reverse end-diastolic flow in either umbilical artery, and known fetal genetic or structural anomalies. The study compared cases with discordant umbilical artery pulsatility index values (defined as 1 umbilical artery pulsatility index at ≤95th percentile and the other umbilical artery pulsatility index at >95th percentile for gestational age) to pregnancies where both umbilical artery pulsatility indices had normal pulsatility index values and those with both umbilical arteries displaying abnormal pulsatility index values. The primary outcome assessed was the occurrence of composite adverse neonatal outcomes. Multivariable logistic regressions were performed, adjusting for relevant covariates., Results: The study encompassed 1014 patients, including 194 patients (19.1%) with discordant umbilical artery pulsatility index values among those who had both umbilical arteries sampled close to delivery, 671 patients (66.2%) with both umbilical arteries having normal pulsatility index values, and 149 patients (14.7%) with both umbilical arteries exhibiting abnormal values. Pregnancies with discordant umbilical artery pulsatility index values displayed compromised sonographic parameters compared with those with both umbilical arteries showing normal pulsatility index values. Similarly, the number of abnormal umbilical artery pulsatility index values was associated with adverse perinatal outcomes in a dose-response manner. Cases with 1 abnormal (discordant) umbilical artery pulsatility index value showed favorable sonographic parameters and perinatal outcomes compared with cases with both abnormal umbilical artery pulsatility index values, and cases with both abnormal umbilical artery pulsatility index values showed worse sonographic parameters and perinatal outcomes compared with cases with discordant UA PI values. Multivariate analysis revealed that discordant umbilical artery pulsatility indices were significantly and independently associated with composite adverse perinatal outcomes, with an adjusted odds ratio of 1.75 (95% confidence interval, 1.24-2.47; P = .002)., Conclusion: Evaluating the resistance indices of both umbilical arteries may provide useful data and assist in assessing adverse perinatal outcomes among fetuses with growth restriction., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The behavior of the pulsatile flow of non-Newtonian micropolar-Casson fluid in a constricted channel influenced by Lorentz force following Darcy's law is examined. The governing model of the problem is transformed into the vorticity-stream function formulation and numerically solved using a scheme based on the finite difference method. Impacts of numerous flow controlling parameters including the Hartmann, Strouhal, porosity, Casson fluid, and micropolar fluid parameters on the wall shear stress (WSS), axial velocity, and micro-rotation velocity are presented graphically and discussed. The WSS is found to increase with rising values of any of the Hartman, Casson fluid, and micropolar fluid parameters. The WSS decreases with rising values of the porosity parameter. The Hartman number is found to have a significant impact on the flow separation region, as well. The velocity profiles are parabolic at all the axial locations. At the constriction throat, the maximum value of the velocity is identified.

Background: Epidemiological studies have shown that women with preeclampsia (PE) are at increased long term cardiovascular risk. This risk might be associated with accelerated vascular ageing process but data on vascular abnormalities in women with PE are scarce., Objective: This study aimed to identify the most discriminatory maternal vascular index in the prediction of PE at 35 to 37 weeks' gestation and to examine the performance of screening for PE by combinations of maternal risk factors and biophysical and biochemical markers at 35 to 37 weeks' gestation., Study Design: This was a prospective observational nonintervention study in women attending a routine hospital visit at 35 0/7 to 36 6/7 weeks' gestation. The visit included recording of maternal demographic characteristics and medical history, vascular indices, and hemodynamic parameters obtained by a noninvasive operator-independent device (pulse wave velocity, augmentation index, cardiac output, stroke volume, central systolic and diastolic blood pressures, total peripheral resistance, and fetal heart rate), mean arterial pressure, uterine artery pulsatility index, and serum concentration of placental growth factor and soluble fms-like tyrosine kinase-1. The performance of screening for delivery with PE at any time and at <3 weeks from assessment using a combination of maternal risk factors and various combinations of biomarkers was determined., Results: The study population consisted of 6746 women with singleton pregnancies, including 176 women (2.6%) who subsequently developed PE. There were 3 main findings. First, in women who developed PE, compared with those who did not, there were higher central systolic and diastolic blood pressures, pulse wave velocity, peripheral vascular resistance, and augmentation index. Second, the most discriminatory indices were systolic and diastolic blood pressures and pulse wave velocity, with poor prediction from the other indices. However, the performance of screening by a combination of maternal risk factors plus mean arterial pressure was at least as high as that of a combination of maternal risk factors plus central systolic and diastolic blood pressures; consequently, in screening for PE, pulse wave velocity, mean arterial pressure, uterine artery pulsatility index, placental growth factor, and soluble fms-like tyrosine kinase-1 were used. Third, in screening for both PE within 3 weeks and PE at any time from assessment, the detection rate at a false-positive rate of 10% of a biophysical test consisting of maternal risk factors plus mean arterial pressure, uterine artery pulsatility index, and pulse wave velocity (PE within 3 weeks: 85.2%; 95% confidence interval, 75.6%-92.1%; PE at any time: 69.9%; 95% confidence interval, 62.5%-76.6%) was not significantly different from a biochemical test using the competing risks model to combine maternal risk factors with placental growth factor and soluble fms-like tyrosine kinase-1 (PE within 3 weeks: 80.2%; 95% confidence interval, 69.9%-88.3%; PE at any time: 64.2%; 95% confidence interval, 56.6%-71.3%), and they were both superior to screening by low placental growth factor concentration (PE within 3 weeks: 53.1%; 95% confidence interval, 41.7%-64.3%; PE at any time: 44.3; 95% confidence interval, 36.8%-52.0%) or high soluble fms-like tyrosine kinase-1-to-placental growth factor concentration ratio (PE within 3 weeks: 65.4%; 95% confidence interval, 54.0%-75.7%; PE at any time: 53.4%; 95% confidence interval, 45.8%-60.9%)., Conclusion: First, increased maternal arterial stiffness preceded the clinical onset of PE. Second, maternal pulse wave velocity at 35 to 37 weeks' gestation in combination with mean arterial pressure and uterine artery pulsatility index provided effective prediction of subsequent development of preeclampsia., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Objectives: COVID-19 has been associated with preterm birth (PTB) and placental-mediated complications, including fetal growth restriction and preeclampsia (PE). This study aimed to estimate the impact of COVID-19 and vaccination on adverse pregnancy outcomes and markers of placental function., Methods: We performed a study on a prospective cohort of women recruited in the first trimester of pregnancy during the early COVID-19 pandemic period (December 2020 to December 2021). At each trimester of pregnancy, the assessment included a questionnaire on COVID-19 and vaccination status; serological tests for COVID-19 (for asymptomatic infection); measurement of placental growth factor (PlGF) and soluble fms-like tyrosine kinase 1 (sFlt-1) in maternal blood; measurement of mean uterine artery pulsatility index (UtA-PI); and pregnancy outcomes (PTB, PE, birth weight below the fifth and the tenth percentile)., Results: Among 788 patients with complete data, we observed 101 (13%) cases of symptomatic infection and 74 (9%) cases of asymptomatic infection with SARS-CoV-2. Most cases (73%) of infection were among women with previous vaccination or COVID-19 infection before pregnancy. COVID-19 infection was not associated with adverse pregnancy outcomes, abnormal fetal growth, sFlt-1/PlGF ratio, or mean UtA-PI. Vaccination during pregnancy did not influence these outcomes either. We observed no case of severe COVID-19 infection requiring respiratory support., Conclusion: Mild symptomatic or asymptomatic COVID-19 during pregnancy did not influence the risk of adverse pregnancy outcomes and the markers of placental function in predominantly vaccinated women. Fetal growth monitoring is unlikely to be mandatory in women with mild symptoms of COVID-19., (Copyright © 2023 The Society of Obstetricians and Gynaecologists of Canada/La Société des obstétriciens et gynécologues du Canada. Published by Elsevier Inc. All rights reserved.)

The study deals with an investigation of the flow of a Bingham plastic fluid in a porous bed under the action of an external magnetic field. Porosity of the bed has been described by considering Brinkman model. Both steady and pulsatile motion of this non-Newtonian fluid have been analysed. The governing equations are solved numerically by developing a suitable finite difference scheme. As an application of the theory in the field of magneto-hemorheology, the said physical variables have been computed by considering the values of the involved parameters for blood flow in a pathological state, when the system is under the action of an external magnetic field. The pathological state corresponds to a situation, where the lumen of an arterial segment has turned into a porous structure due to formation of blood clots. Numerical estimates are obtained for the velocity profile and volumetric flow rate of blood, as well as for the shear stress, in the case of blood flow in a diseased artery, both the velocity and volumetric flow rate diminish, as the strength of the external magnetic field is enhanced. The study further shows that blood velocity is maximum in the plug (core) region. It decreases monotonically as the particles of blood travel towards the wall. The study also bears the potential of providing numerical estimates for many industrial fluids that follow Bingham plastic model, when the values of different parameters are chosen appropriately.

Aiming to experimentally investigate the effect of aspect ratio (AR) of image-based aneurysm on wall deformation oscillation under different pulsatile flow conditions with considering the fluid-structure interaction. In this study, three silicon aneurysm models with different AR (0.8, 1.0, and 1.2) were constructed. It was found that the detected wall deformation oscillation of patient-specific aneurysm increased with pulsatile inflow frequency increases, which was greater and more obvious oscillation than that in the ideal lateral aneurysm. In addition, the maximum amplitude of wall deformations oscillation of the aneurysm at the dome during the systolic phase decrease and the oscillation of wall deformation become obvious as AR increases. These results could provide more knowledge about the effect of AR and pulsatile flow on the wall deformation of aneurysm and will be helpful for understanding the aneurysm rupture risk.

Based on the generalized Darcy model, here we develop a linear one-dimensional (1D) composite model to predict the effects of the inserted balloon under REBOA operations on the dynamic characteristics of blood flow in flexible arterial networks. We first consider the effect of the decrease of cardiac output under different degrees of blood loss through employing the fourth-order lumped parameter model of cardiovascular system. Then, the effect of the inserted balloon is included by developing the relation between flow resistance and occlusion ratio with the neural network approach. Finally, the accuracy of the developed 1D composite model for REBOA operations, which can be solved analytically in the frequency domain, is verified by comparing to computational fluid dynamics (CFD) simulations. It is demonstrated that the 1D model is able to reproduce main features of the systemic circulation under balloon occlusion of the aorta during REBOA surgery. The 1D composite model could substantially reduce the computational time, which makes it possible to give the instant prediction of the working parameters during RABOA operations., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Purposes: 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., Methods: Flow quantification was assessed using a pulsatile flow phantom (diameter: 9.5 mm; mean flow rate: 1150 mm 3 /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., Results: 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)., Conclusions: 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., Competing Interests: Declaration of competing interest The authors declare that they have no conflicts of interest with respect to the research, authorship, and/or publication of this article. The figures are original and have not been published previously., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Fluid recirculation is an important function for organ-on-chip and microfluidic applications. For a systematic analysis, simultaneously applying multi-flow conditions in parallel channels is essential. However, control of parallel recirculation flows without using dynamic off-chip controllers that can drastically simplify device operation has been rarely implemented. In this study, we develop a microfluidic recirculation system driven only by water-head pressures. The pressures generated by reservoirs with <500 mL water volumes drive the system and recirculate <500 μL cell culture media volumes. The system realizes media recirculation in its four parallel channels with pulsatile and constant flows in a preprogrammed manner. The system, which consists of oscillator and cell culture modules, controls the flow rates and shear stress in wide ranges of 0.06-144 μL min -1 and 0.004-9.6 dyn cm -2 , respectively. For pulsatile flows, the pulse period is independent of the flow rate and varies in the range of 0.7-13.0 s. To demonstrate the utility of the device, the systematic and parallel analysis of endothelial cell elongation response to different fluidic shearing patterns is performed. In addition, the culture of myoblasts is illustrated, and myotube formation is successfully obtained for 8 days., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)