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We investigate the formation and transport of gas bubbles across a model porous electrode/catalyst using lattice Boltzmann simulations. This approach enables us to systematically examine the influence of a wide range of morphologies, flow velocities, and reaction rates on the efficiency of gas production. By exploring these parameters, we identify critical parameter combinations that significantly contribute to an enhanced yield of gas output. Our simulations reveal the existence of an optimal pore geometry for which the product output is maximized. Intriguingly, we also observe that lower flow velocities improve gas production by leveraging coalescence-induced bubble detachment from the electrode/catalyst. [ABSTRACT FROM AUTHOR]

Fluid-based methods for particle sorting demonstrate increasing appeal in many areas of biosciences due to their biocompatibility and cost-effectiveness. Herein, we construct a microfluidic sorting system based on a swirl microchip. The impact of microchannel velocity on the swirl stagnation point as well as particle movement is analyzed through simulation and experiment. Moreover, the quantitative mapping relationship between flow velocity and particle position distribution is established. With this foundation established, a particle sorting method based on swirl induction is proposed. Initially, the particle is captured by a swirl. Then, the Sorting Region into which the particle aims to enter is determined according to the sorting condition and particle characteristic. Subsequently, the velocities of the microchannels are adjusted to control the swirl, which will induce the particle to enter its corresponding Induction Region. Thereafter, the velocities are adjusted again to change the fluid field and drive the particle into a predetermined Sorting Region, hence the sorting is accomplished. We have extensively conducted experiments taking particle size or color as a sorting condition. An outstanding sorting success rate of 98.75% is achieved when dealing with particles within the size range of tens to hundreds of micrometers in radius, which certifies the effectiveness of the proposed sorting method. Compared to the existing sorting techniques, the proposed method offers greater flexibility. The adjustment of sorting conditions or particle parameters no longer requires complex chip redesign, because such sorting tasks can be successfully realized through simple microchannel velocities control. [ABSTRACT FROM AUTHOR]

Directional fluid flow in perivascular spaces surrounding cerebral arteries is hypothesized to play a key role in brain solute transport and clearance. While various drivers for a pulsatile flow, such as cardiac or respiratory pulsations, are well quantified, the question remains as to which mechanisms could induce a directional flow within physiological regimes. To address this question, we develop theoretical and numerical reduced-order models to quantify the directional (net) flow induceable by peristaltic pumping in periarterial networks. Each periarterial element is modeled as a slender annular space bounded internally by a circular tube supporting a periodic traveling (peristaltic) wave. Under reasonable assumptions of a small Reynolds number flow, small radii, and small-amplitude peristaltic waves, we use lubrication theory and regular perturbation methods to derive theoretical expressions for the directional net flow and pressure distribution in the perivascular network. The reduced model is used to derive closed-form analytical expressions for the net flow for simple network configurations of interest, including single elements, two elements in tandem, and a three element bifurcation, with results compared with numerical predictions. In particular, we provide a computable theoretical estimate of the net flow induced by peristaltic motion in perivascular networks as a function of physiological parameters, notably, wave length, frequency, amplitude, and perivascular dimensions. Quantifying the maximal net flow for specific physiological regimes, we find that vasomotion may induce net pial periarterial flow velocities on the order of a few to tens of μ m/s and that sleep-related changes in vasomotion pulsatility may drive a threefold flow increase. [ABSTRACT FROM AUTHOR]

Summary: Characteristic of all conifer needles, the transfusion tissue mediates the radial transport of water and sugar between the endodermis and axial vasculature. Physical constraints imposed by the needle's linear geometry introduce two potential extravascular bottlenecks where the opposition of sugar and water flows may frustrate sugar export: one at the vascular access point and the other at the endodermis.We developed a network model of the transfusion tissue to explore how its structure and composition affect the delivery of sugars to the axial phloem. To describe extravascular transport with cellular resolution, we construct networks from images of Pinus pinea needles obtained through tomographic microscopy, as well as fluorescence and electron microscopy.The transfusion tissue provides physically distinct pathways for sugar and water, reducing resistance between the vasculature and endodermis and mitigating flow constriction at the vascular flank. Dissipation of flow velocities through the transfusion tissue's branched structure allows for bidirectional transport of an inbound diffusive sugar flux against an outbound advective water flux across the endodermis.Our results clarify the structure–function relationships of the transfusion tissue under conditions free of physiological stress. The presented model framework is also applicable to different transfusion tissue morphologies in other gymnosperms. [ABSTRACT FROM AUTHOR]

Among all the factors affecting the destructiveness of debris flow, the mean velocity is one of the most important characteristics. In this paper, we aim to apply a particle swarm optimization (PSO) based on the relevance vector machine (RVM) to predict the mean velocity. The PSO is used to optimize kernel parameters inside the RVM, whereas the RVM is responsible for completing the prediction task. Through sample training, a nonlinear relationship can be obtained, enabling a rapid prediction of the mean velocity for new samples. The debris flow dataset of Jiangjia Gully is used to evaluate the performance of PSO‐RVM in this study. Besides, we further compare the prediction results of PSO‐RVM with other prominent approaches, for example, the support vector machine (SVM), BP neural network (BP), and the RVM. The results show that the mean relative error (MRE) of PSO‐RVM is only 0.69%. In addition, BP yields the highest MRE (27.61%), and the MRE (2.75%) corresponding to the RVM is lower than that (5.98%) yielded by the SVM. For the root mean square error (RMSE) and Theil's inequality coefficient (TIC), the PSO‐RVM method still generates much lower RMSE (6.48%) and TIC (0.179%) values than the other three methods. Overall, compared with current debris flow prediction models, the PSO‐RVM achieves high prediction accuracy, fewer optimization parameters, and low computational complexity. Finally, a sensitivity analysis is conducted to explore the dominative factors of debris flow. [ABSTRACT FROM AUTHOR]

This work reports experimental results from laminar-to-turbulent lifted jet diffusion flames. Characteristics of flame liftoff height, flame base structure, cold and reacting jet flow fields, and velocity fields near the flame base during the transitional process were obtained. The flame transition and stabilization characteristics are the focus of the present study. Results show that the lifted flame transition is mainly caused by the interaction between turbulent jets and flame base. As the transition begins, folding and distortion of the flame base occur. With the increase in Reynolds number (Re), the extent to which flame base is distorted increases constantly due to influences of more vortices. Simultaneously, at this transitional stage, the liftoff height decreases with Re. At different co-flow air velocities (Uair), the mean liftoff height with Re are qualitatively the same. While as Uair is increased, the critical transitional Reynolds number (in which the flame transition begins) decreases. In the later transitional regime within a range of Re, both the cold and reacting jets exhibit intermittent breakup. After jet breakup, flame base immediately becomes turbulent. When the intermittent flow in the transitional stage gradually becomes less turbulent, flame base still remains turbulent for some time, within which flame and flow can be evidently decoupled. By statistical analysis, the integral length scale and the root mean square (r.m.s.) velocity fluctuation near the lifted flame base were obtained, and then the turbulent flame speed can be estimated. Experimental evidence provided for stabilization mechanism of the original transitional flames was confirmed by the balance between the local flow velocity and the flame speed. However, the difference between the two velocities gradually increases with the Reynolds number, suggesting some new stabilization characteristics. When the upstream eddy contains flammable fuel/air mixture, the flame base responds with moving upstream after ignition. On the contrary, when the mixture in the eddy is nonflammable, the flame base would move downstream. [ABSTRACT FROM AUTHOR]

The combustion of flexible polyurethane foam (FPUF) poses a significant fire safety risk due to the flow and dropping behavior of its liquid products, which can accelerate fire growth and spread between nonadjacent objects. In this work, the formation, flow, and dropping phenomena of FPUF liquid products were investigated in the laboratory. The findings show that the polyols pyrolyzed by FPUF initially form bead-like droplets on the foam surface, which undergo a morphological transformation from spherical to hemispherical and striped shapes on the side of the foam. The downward flow velocity of the largest droplet is measured to be 5.3 ± 0.4 mm s−1. Furthermore, it is found that droplets with diameters less than 0.70 mm float up, while droplets above the critical dropping diameter have a high risk of igniting flammable materials below. The critical dropping diameter increases linearly with the drop height. These results contribute to a better understanding of the behavior of FPUF during combustion and have important implications for fire safety engineering. [ABSTRACT FROM AUTHOR]

This study implements an entropy theory-based approach to infer bathymetry for 29 selected cross-sections along a 1740 km reach of the Congo River. A genetic algorithm optimization approach is used based on an analysis of near-surface velocity measurements to generate a random sample of 1000 bathymetry profiles from which the analysis is carried out. The resulting simulated bathymetry shows good agreement compared to the measurements obtained via Accoustic Doppler Current Profiler (ADCP), with a correlation that varies from 0.49 to 0.88. The bathymetry results are subsequently used to estimate the two-dimensional cross-sectional flow velocity distribution and, consequently, to calculate the river discharge. The mean errors observed for flow area, discharge, and mean velocity are found to be 2.7%, 1.3%, and 1%, respectively. This study demonstrates, for the first time, the successful application of an entropy-based approach to estimate bathymetry and discharge in large rivers and has significant implications for remote sensing applications. [ABSTRACT FROM AUTHOR]

This research examines the influence of peak time, flood duration, and pier position on the variations in scour pattern and the greatest depth of scour cavity surrounding a single pier protected with a collar. The study encompasses a flow velocity range spanning from incipient motion conditions to mobile bed conditions. The findings demonstrate that the implementation of a collar not only reduces the dimensions of the scour cavity surrounding the piers but also alters the location of the greatest depth of scour cavity. On average, the utilization of a collar at 60°, 90°, and 120° positions during four flood durations resulted in respective reductions of 40%, 60%, and 45% in the average scour cavity volumes surrounding the pier. Results further indicate that the collar successfully reduced the greatest depth of scour cavity, volume, and area surrounding the pier in over 95% of the conducted tests. [ABSTRACT FROM AUTHOR]

The present study conducts an experimental investigation into the flow characteristics over a cascade of both slotted and non-slotted compressor blades. The focus is on evaluating potential statistical correlations between higher-order moments of velocity fluctuations, including Skewness and Kurtosis. The linear axial cascade comprises three NACA6409 blades, which are tested in both normal and slotted blade. Data acquisition was conducted using a hot wire anemometer at three measurement stations within the cascade. The hot wire sensor was positioned at distances of x/c = 0.125, 0.25, and 0.5 from the trailing edge (x), where x represents the distance from the probe to the trailing edge of the airfoil and (c) is the chord length of the blade. Measurements were taken at a blade angle of attack of 0° and two Reynolds numbers: 22,750 and 45,500. Results indicate that blade grooving enhances flow velocity, postpones separation and improves flow control in the trailing edge region. By comparing calculated Skewness and Kurtosis values with those predicted by existing boundary layer and free jet relations, more consistent correlations were identified. To provide more accurate relationships, two polynomials of the second and third order have been used. It was found that high-order values of velocity were obtained more accurately with the relations presented in this research. Although the accuracy of these predictions is significantly reduced in the proportion of larger distances. In distant stations, the loss velocity has decreased. As the distance from the model increases, the amount of inhomogeneities in the sequence increases and the values of the opposite Skewness become zero. Turbulence intensity has been reduced by slotting the blades. [ABSTRACT FROM AUTHOR]

Submerged macrophytes have complex effects on spatiotemporal characteristics of river ecosystems, including trout habitat. We investigated the impact of submerged macrophyte coverage on trout habitat in the Henrys Fork of the Snake River, Idaho, USA. We hypothesized that higher submerged macrophyte coverage would create new habitat types beneficial for trout growth. We assessed river physical and biotic attributes, trout habitat preferences, and estimated trout growth potential with bioenergetics models across a gradient of submerged macrophyte coverage (32–94%). We identified four distinct habitat types within the riverscape shaped by submerged macrophyte coverage. Increased submerged macrophyte coverage increased the frequency of habitat types with higher trout growth potential but reduced the occurrence of preferred habitat types. We observed no relationship between reach-scale trout growth potential and submerged macrophyte coverage. However, an outlier of very high trout growth potential at 94% submerged macrophyte coverage suggests a potential threshold effect. More study is required but our observations suggest macrophyte growth homogenized physical habitat characteristics, reduced flow velocities, and increased invertebrate drift, thereby enhancing trout growth potential. Our findings underscore the complex interplay between submerged macrophytes and trout habitat dynamics across scales, emphasizing the importance of considering both physical and biological effects on trout habitat. [ABSTRACT FROM AUTHOR]

• A model for predicting the performance of rotor-only axial fans, given the tangential flow velocity distribution, was proposed. • Using this model, a screening of possible solutions was carried out to find a design that provides maximum efficiency, and another with maximum flow. • The results were compared with the free-swirl methodology. • The designed fans were prototyped through 3D printing and their results were compared with a commercially used model. • The fan for maximum efficiency obtained a gain of 11 % while the one for maximum flow obtained a gain of 10 %. The paper puts forward a computer methodology for designing low-pressure axial fan blades for small-capacity refrigeration applications. Based on the blade element theory (BET), the airfoil efficiency of the airfoil, the principles of mass and momentum conservation together with empirical correlations for the flow irreversibilities, a mathematical model was devised for screening the blade geometric parameters (e.g., radial chord and pitch variation, and hub radius) by varying the induction coefficient distribution for a given fan diameter, motor speed, and airflow system characteristic curve. The best blade configuration is selected by means of a tailor-made optimization algorithm and undergoes a series of linear transformations for translating the fan parametrization into a CAD drawing. Two new fan blades were designed, one for maximum blade efficiency (MBE) and another for maximum airflow rate (MAR). In comparison with the free-swirl design approach, a standard procedure adopted in the open literature, the proposed blades showed an efficiency and an airflow by 20 % (MBE) and 14 % (MAR) higher than the reference. The airflow characteristics of the new designs were also assessed by means of wind-tunnel testing, which confirmed an increase of 11 % in the case of MBE design, while an enhancement of 10 % was observed in the case of MAR design. [ABSTRACT FROM AUTHOR]

Orthostatic intolerance (OI) is a common problem. Reliable markers of OI are missing, as orthostatic blood pressure and heart rate poorly correlate with orthostatic symptoms. The objective of this study was to assess the relationship between orthostatic lightheadedness and cerebral blood flow. In this retrospective study patients with OI were evaluated at the Autonomic Laboratory of the Department of Neurology, Brigham and Women's Faulkner Hospital, Boston. The 10-minute head-up tilt test was performed as a part of autonomic testing. Orthostatic lightheadedness was evaluated at every minute of the head-up tilt. Heart rate, blood pressure, capnography, and cerebral blood flow velocity (CBFv) in the middle cerebral artery using transcranial Doppler were measured. Repeated-measures design with a linear mixed-effects model was used to evaluate the relationship between orthostatic lightheadedness and hemodynamic variables. Correlation analyses were done by calculating Pearson's coefficient. Twenty-two patients with OI were compared to nineteen controls. Orthostatic CBFv and end-tidal CO2 decreased in OI patients compared to controls (p < 0.001) and predicted orthostatic lightheadedness. Orthostatic heart rate and blood pressure failed to predict orthostatic lightheadedness. The lightheadedness threshold, which marked the onset of lightheadedness, was equal to an average systolic CBFv decrease of 18.92% and end-tidal CO2 of 12.82%. The intensity of lightheadedness was proportional to the CBFv and end-tidal CO2 decline. Orthostatic lightheadedness correlated with systolic CBFv (r=-0.6, p < 0.001) and end-tidal CO2 (r=-0.33, p < 0.001) decline. In conclusion, orthostatic CBFv and end-tidal CO2 changes predict orthostatic lightheadedness and can be used as objective markers of OI. [ABSTRACT FROM AUTHOR]

In this study, dynamic properties of fluid-conveying flexoelectric cylindrical nanoshells subjected to an electric field are examined throughout the wave propagation approach. Employing nonlocal strain gradient theory (NSGT) and constitutive flexoelectric relations for shell-type structure, a new model has been represented regarding the Love shell theory. Governing motion equations are derived exploiting Hamilton's principle and are then solved numerically to acquire the wave propagation properties. A discussion on numerical results is then implemented to highlight the exact wave propagation response of the structure against the flexoelectric effect, electric field, flow velocity and external force. The results reveal a remarkable effect of flexoelectricity on wave propagation response especially for some modes in specific wave number domains. As a prominent result, the flexoelectricity effect on wave dispersion response is found more pronounced for second and third modes, compared to the first mode. In addition, this effect is more tangible for lower wave numbers. The applied positive or negative electric and mechanical force exhibits a decreasing or increasing effect on the phase velocity of all the modes. The presented investigation and the reported results may be useful in designing the systems which are benefiting from wave propagation phenomenon properties of cylindrical nanoshells. [ABSTRACT FROM AUTHOR]

Solar air heaters (SAHs) are widely used for drying vegetables and fruits or for domestic heating. Certain sizing parameters are necessary to obtain the right dimensions for the required air temperature, flow rate, and thus useful thermal energy. The well‐known Hottel–Whillier–Bliss equation was used and made dimensionless by applying the collector longitudinal and transversal aspect ratios (rl and rt) of a double‐glazed flat plate solar air heater (DG‐FPSAH). The steady‐state equations are solved to determine the average temperatures. Thereafter, one could calculate the overall loss heat coefficient and efficiency factor, obtained analytically. A Matlab code was developed to estimate primarily unknown temperatures, useful energy, and the Nusselt number. An iterative numerical method is used until convergence occurs. The inlet cross‐sectional area and air flow velocity are defined as input data. The proposed sizing method depends on the output temperature required by the customer. This temperature can be determined from the plotted curves of the dimensionless ratios. Hence, the SAH‐needed dimensions are determined graphically depending on the functional requirements for construction planning, such as technology choice, work breakdown, and budgeting. In the present case study, based on the input parameters, an airflow rate of 1.2 kg/s entering a DG‐FPSAH with an output temperature of 41.5°C yields the dimensions of Lin = 3.824 m, Win = 2.735 m, and Hin = 0.1825, specifying the collector length, width, and air duct height. The gathered energy and thermohydraulic efficiency are: Qu = 7.91 kW, ηcol = 0.752, respectively. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the transient dynamics of a third-grade fluid, which can undergo exothermic reactions in a saturated porous microchannel. The adverse pressure gradient force constitutes the primary flow driver. In addition to exothermic reactions, the system is also subjected convective cooling at the microchannel boundaries. Newton's law of cooling and Arrhenius kinetics are employed to model the boundary cooling and exothermic reactions, respectively. The temperature-dependent fluid viscosity is modelled via a Nahme-type law and the porous material between the parallel microchannels is assumed to have constant permeability. To account for this, the unsteady modified Darcy's law is applied, effectively capturing the impact of porosity. Computational solutions are employed to solve the non-homogeneous partial differential equations (PDEs) for the flow temperature and velocity. These computational solutions are developed from efficient, convergent and unconditionally stable, semi-implicit finite difference (SIFD) methods. Examining the thermodynamic and fluid-dynamical consequences of variations in the numerical exponent ℵ and exothermic reaction parameter δ 2 are the principal motives of the study. A comparative evaluation of the thermal runaway susceptibility of the numerical exponent parameter for two distinct types of fluids is outlined, indicating that the ranking of susceptibility ranges from most to least susceptible in the bimolecular case, the Arrhenius case and the sensitised case. Newtonian fluids are the most prone to non-Newtonian fluids. Additionally, the study systematically explores the sensitivity of field variables to changes in different flow parameters through graphical representations and shows that the fluid variables increase with the increase in Reynolds number, viscosity parameter and Brinkman number, while decrease for the third-order parameter and porous medium parameter. The obtained results are qualitatively discussed and compared with the published data. [ABSTRACT FROM AUTHOR]

A non-linear critical layer analysis of the presence of singular azimuthal neutral modes in density stratified swirling flows is considered. It is shown that finite amplitude neutral modes exist when the basic flow velocity, vorticity, and temperature profiles undergo distortions with the occurrence of jump in them. [ABSTRACT FROM AUTHOR]

Understanding the flow pressure distribution on the blade airfoil of the tidal turbine is of great significance for optimising the energy harvesting performance of the blades. In this paper, a bidirectional type horizontal tidal turbine (BHTT) with special S-shaped blades is proposed, which have a larger pitch diameter ratio provide excellent performance at low oncoming flow velocity by the theoretical, numerical and experimental methods. First, it is verified that the energy harvesting efficiency is basically the same in the case of bidirectional flow, and the S-shaped blade is divided into multiple slice sections, which could quantify the energy harvesting performance of each area of the blade. Then, using the method of mathematical statistics to divide more areas, the probability density shows a skewed distribution. The results show that the energy harvesting performance is less affected by flow velocity fluctuation, and the energy harvesting efficiency could reach 0.25-0.55 when the tip speed ratio is in the range of 0.2-0.5. Furthermore, the slice section method is adopted to make the influence of axial thrust intuitive and clear to study the turbine energy harvesting performance and improve the harvesting efficiency, which could provide a reference for the engineering design of tidal turbines. [ABSTRACT FROM AUTHOR]

BACKGROUND: Delayed cord clamping is the standard of care for both term and preterm infants worldwide. The aim of this study was to evaluate the effect of 60-second or 180-second delayed cord clamping during labor on cerebral oxygenation and cardiac function. METHODS: Healthy newborns were divided into two groups: a 60-second delay in cord clamping (60-s DCC) and a 180-second delay in cord clamping (180-s DCC) at birth. Pulse oximetry and cerebral near-infrared spectroscopy (cNIRS) probes were placed during postnatal care. A total of 84 healthy newborns were included in this study. Preductal oxygen saturation (SpO2), heart rate, and cNIRS values were recorded at 5 and 10 minutes after delivery. The cardiac function of the infants was assessed by echocardiography at 3–7 days postnatally. RESULTS: There was no significant difference between the groups in SpO2 and cNIRS values at 5 and 10 min. While there was no significant difference in the number of neonates with targeted SpO2 at the 5th and 10th min and targeted cNIRS values at the 10th min, there was a significant difference in the number of neonates with target cNIRS values at the 5th min between groups (p < 0.001). Echocardiographic findings showed that pulmonary flow velocity was increased in the 180-s DCC group; the difference was statistically significant (p = 0.04). CONCLUSION: Our results showed that the number of infants with normal cNIRS values regarding cerebral oxygenation was higher in the 180-s DCC group. The pulmonary flow velocity was significantly increased in the 180-s DCC group in terms of echocardiographic findings. [ABSTRACT FROM AUTHOR]

A sudden angle change between the Y-shaped diversion channel and the inlet tank of the circular pump station often leads to boundary layer separation and large vortex formation. These flow patterns can cause significant sediment deposition in sediment-laden rivers, reducing pump efficiency. A mixture model is introduced to describe water-sediment two-phase flows. Simulation results analyze vortex characteristics and formation mechanisms, and evaluate potential sediment deposition areas. Without rectification, vortex areas cause significant sediment migration towards the sidewalls of the Y-shaped diversion channel and pump inlet. Diversion measures like sills and pressure plates are introduced to reduce flow vortices. Results show that sills generally optimize flow structures. Sills in the main Y-shaped diversion channel outperform those in other channels in terms of optimization. Pressure plates also optimize flow structures. Vortex structure and position are closely related to the distance between the pressure plate and the circular intake tank. Optimized measures with pressure plates significantly reduce the flow deviation angle and improve flow velocity uniformity. Numerical simulation accuracy is validated through experiments. Results reveal the formation mechanism of adverse vortices and their sedimentation effects, which are detrimental to pump stations. The proposed rectification scheme provides theoretical support for optimizing pump station operation. [ABSTRACT FROM AUTHOR]

An express method for evaluating water discharge based on calculating surface water flow velocity with the use of PIV-method is considered. A procedure of measurements and an algorithm of software for processing video images of water flow are demonstrated. The results of field studies with the use of the proposed method are presented and compared with those obtained by standard procedures. The proposed method gives real-time data on water discharge in a river or canal without the need to use expensive measurement instruments and trained personnel. The method gives flow velocity field all over the cross section of the studied water body, thus providing more accurate data on water discharge than standard measurement instruments (hydrometers, float method) used in individual points at certain stations. The obtained data on water discharge can be used for scientific substantiation of works for designing bank-protection, channel-regulating marine and river structures, as well as for environmental assessment of the state of a water object at studying water pollution problems. The use of the proposed method at hydrological gages in operation will enable promptly determining water discharge in rivers in a remote regime with the use of appropriate equipment, which is of particular importance for Crimea for assessing peak flow in periods of high freshets and spring floods. [ABSTRACT FROM AUTHOR]

Fluorescent tuft visualization technology, as a practical and convenient technique, has attracted widespread attention. In this study, a novel fluorescent tuft velocity measurement method is developed based on existing technologies. This method involves the recognition of tuft deflection angles, image transformation, block processing, temporal averaging, and post-visualization processing. Additionally, quantitative measurement of flow field velocity is achieved through tuft calibration. The study begins by comparing tufts of different materials, examining both fluorescent and deflection characteristics to determine optimal tuft parameters. The impact of tuft length on deflection characteristics is also investigated. Finally, the cotton tuft with a length of 7 mm and a diameter of about 0.1 mm was obtained as the best tuft sought in this experiment. Subsequently, at Reynolds number Re = 1.7 × 105, airfoil surface flow field visualization and quantitative analysis are conducted, exploring the relationship between airfoil surface flow structure and aerodynamics at different angles of attack. Finally, a comparative study is conducted between tuft velocity results and oil flow visualization experiments, as well as particle image velocimetry experiments, confirming the feasibility of the fluorescent tuft velocity measurement method. [ABSTRACT FROM AUTHOR]

Background: Portal vein thrombosis (PVT) is thought to arise from stagnant blood flow, yet conclusive evidence is lacking. Relative residence time (RRT) assessed using 4D Flow MRI may offer insight into portal flow stagnation. Purpose: To explore the relationship between RRT values and the presence of PVT in cirrhotic participants. Study Type: Prospective. Population: Forty‐eight participants with liver cirrhosis (27 males, median age 67 years [IQR: 57–73]) and 20 healthy control participants (12 males, median age 45 years [IQR: 40–54]). Field Strength/Sequence: 3 T/4D Flow MRI. Assessment: Laboratory (liver and kidney function test results and platelet count) and clinical data (presence of tumors and other imaging findings), and portal hemodynamics derived from 4D Flow MRI (spatiotemporally averaged RRT [RRT‐mean], flow velocity, and flow rate) were analyzed. Statistical Tests: We used multivariable logistic regression, adjusted by selected covariates through the Lasso method, to explore whether RRT‐mean is an independent risk factor for PVT. The area under the ROC curve (AUC) was also calculated to assess the model's discriminative ability. P < 0.05 indicated statistical significance. Results: The liver cirrhosis group consisted of 16 participants with PVT and 32 without PVT. Higher RRT‐mean values (odds ratio [OR] 11.4 [95% CI: 2.19, 118]) and lower platelet count (OR 0.98 per 1000 μL [95% CI: 0.96, 0.99]) were independent risk factors for PVT. The incorporation of RRT‐mean (AUC, 0.77) alongside platelet count (AUC, 0.75) resulted in an AUC of 0.84. When including healthy control participants, RRT‐mean had an adjusted OR of 12.4 and the AUC of the combined model (RRT‐mean and platelet count) was 0.90. Data Conclusion: Prolonged RRT values and low platelet count were significantly associated with the presence of PVT in cirrhotic participants. RRT values derived from 4D Flow MRI may have potential clinical relevance in the management of PVT. Evidence Level: 2 Technical Efficacy: Stage 2 [ABSTRACT FROM AUTHOR]

Cerebrospinal fluid (CSF) circulation plays a key role in cerebral waste clearance via the glymphatic system. Although CSF flow velocity is an essential component of CSF dynamics, it has not been sufficiently characterized, and particularly, in studies of the glymphatic system in rat. To investigate the relationship between the flow velocity of CSF in the brain aqueduct and the glymphatic waste clearance rate, using phase‐contrast MRI we performed the first measurements of CSF velocity in rats. Phase‐contrast MRI was performed using a 7 T system to map mean velocity of CSF flow in the aqueduct in rat brain. The effects of age (3 months old versus 18 months old), gender, strain (Wistar, RNU, Dark Agouti), anesthetic agents (isoflurane versus dexmedetomidine), and neurodegenerative disorder (Alzheimer' disease in Fischer TgF344‐AD rats, males and females) on CSF velocity were investigated in eight independent groups of rats (12 rats per group). Our results demonstrated that quantitative velocities of CSF flow in the aqueduct averaged 5.16 ± 0.86 mm/s in healthy young adult male Wistar rats. CSF flow velocity in the aqueduct was not altered by rat gender, strain, and the employed anesthetic agents in all rats, also age in the female rats. However, aged (18 months) Wistar male rats exhibited significantly reduced the CSF flow velocity in the aqueduct (4.31 ± 1.08 mm/s). In addition, Alzheimer's disease further reduced the CSF flow velocity in the aqueduct of male and female rats. [ABSTRACT FROM AUTHOR]

Eddies assume a pivotal role in both the oceanic heat cycle and marine dynamic processes. The development of real-time satellite observations, coupled with advancements in computer intelligence, has propelled automatic eddy detection algorithms to the forefront of ocean remote sensing research. Nevertheless, target omissions and accuracy degradations are inevitable for multiple detection algorithms due to strong morphological variations in ocean eddies. This paper proposes an automatic detection algorithm based on the quadrant angle of the velocity vector in the flow field. Firstly, a rectangular search box is established, and the corresponding quadrant angles at the four vertices are calculated. Secondly, the centres and types of eddies are determined according to the cumulative sum and variety rules of quadrant angles. Then the outermost boundary is identified by regularity of quadrant angles in eight directions expanding outward from the centre of the eddy using the stream function equation. The new algorithm is assessed and verified using geostrophic flow data derived from the CMEMS standard gridded sea level anomaly product. Furthermore, its detection capabilities are demonstrated through a comparative analysis with several other algorithms. All methods exhibit consistent efficacy in detecting the majority of eddies with similar spatial distributions. In cases where the new algorithm identifies a specific eddy not detected by the FF15 and ND10 algorithms, sea surface temperature data is employed for verification. The sea surface temperature distribution map, along with the obtained results, illustrates the superiority of the new algorithm and its adaptability to products with varying resolutions. Additionally, the results undergo verification through a manual detection method, revealing that the new algorithm achieves SDR of 91.73% and an EDR of 3.54%. This percentage significantly surpasses the lower acceptable limit of 80% for the SDR parameter. The new algorithm is applied to study eddies with lifetimes exceeding ten days, spanning from March 2022 to February 2023, within the East China Sea and the South China Sea. The radius of SCS eddies is generally larger than that of ECS eddies, both cyclonic and anticyclonic. This further confirms the significant influence of regional ocean dynamics on the structure of eddies in different regions. Finally, the algorithm is applied to SWOT data to test the adaptability of the algorithm to non-regular grid data. The results show that the algorithm can effectively analyse SWOT data within 60° latitudes. [ABSTRACT FROM AUTHOR]

ABSTRACT Sound is critical in fish behaviours, including reproduction, feeding, predator avoidance and habitat selection. To investigate the impact of underwater soundscape on the distribution of Cobitidae fishes, we surveyed the status of Cobitidae fish resources and the underwater soundscape along with related environmental factors at 12 sampling sites downstream of the Songxin Hydropower Station in the Heishui River, a major tributary of the Jinsha River in China. Generalised additive models (GAMs) were employed to identify the primary environmental factors influencing the distribution of Cobitidae fishes and we analysed the correlation between the abundance of Cobitidae fish and primary environmental factors. The study revealed that the water depth, flow velocity, water temperature and sound pressure level (SPL) all had highly significant effects on the distribution of Cobitidae fishes (p < 0.001), with SPL showing the lowest relative importance among these factors. Water depth positively correlated with Cobitidae fish abundance, whereas water temperature, SPL and flow velocity showed negative correlations. This study preliminarily explored the response relationship between the distribution of Cobitidae fish and four main environmental factors, offering a technical foundation for predicting the distribution of Cobitidae fishes in rivers and for implementing conservation measures of fish such as suitable habitat creation. [ABSTRACT FROM AUTHOR]

The glymphatic system of fluid flow through brain tissue may clear amyloid-β during sleep and as such underlie the need for sleep. Dysfunctional glymphatic transport has been implicated in pathological conditions ranging from stroke and dementia to psychiatric illnesses. To date, the fastest observed in-vivo brain flows have been reported after the manipulation of blood osmotic pressures. Surprisingly, the brain seems to shrink while receiving more influx. Though influx of an incompressible fluid might expand the tissue, no physical theory for these observations has been proposed. We here present a minimal mathematical model of brain pressure, deformation, and fluid flows due to vascular osmotic pressures. The model is based on Darcy flow, linear poroelasticity theory and conservation of mass. We propose that a screened Poisson equation holds for interstitial pressure because vascular filtration corresponds to fluid divergence. The model resolves the apparent paradox of combined fluid influx with tissue shrinkage by showing that fluid absorption into the blood can drive both. In this model, small glucose concentration differences between plasma and brain can drive brain flow velocities observed in recent in-vivo assays. Osmosis may therefore drive brain fluid flow under physiological conditions and provide an explanation for the known correlations between diabetes and dementia. [ABSTRACT FROM AUTHOR]

ABSTRACT Flow‐accelerated corrosion (FAC) is a complex phenomenon that poses a significant threat to the integrity of piping and fittings in power plants, affecting infrastructure protection and power production reliability. The presence of corrosive substances in the fluid and elevated flow velocity and temperature leads to increased material loss in piping and equipment. Understanding the intricate relationship among the contributing factors such as flow dynamics, environmental factors, and corrosion reactions is essential for developing effective prediction and mitigation strategies. This review discusses the recent advancements in the numerical modeling of FAC using computational fluid dynamics (CFD). The numerical models presented show abilities to predict FAC profiles across multiple power plant components, and a review was conducted on the evaluation of these predictions with experimental measurements. Notably, increased turbulence in the flow significantly contributed to prediction errors, emphasizing the need for advanced turbulence models in numerical simulations of FAC. Addressing these challenges is crucial for maintaining sustainable infrastructure and reducing industrial risks through enhanced predictive maintenance strategies. [ABSTRACT FROM AUTHOR]

Flow and environmental dispersion are necessary in water management systems. To better understand contaminant transport in wetland flows with adjacent aquatic vegetation and riparian buffers, a two-zone-model wetland is considered to characterize the water flow and environmental dispersion. Many researchers developed a dispersion model to characterize the mean concentration subject to the first-order degradation effect, present study attempts to derive an analytical dispersion model to discuss the transverse mean concentration of pollutants subject to second-order degradation effects in a width-dominated wetland flow. In addition, this study attempts to highlight the effect of environmental parameters like vegetation, viscous friction, and relative width on flow velocity. Also, the transverse mean concentration in the longitudinal direction is derived based on Mei’s multi-scale perturbation approach and analyzed with different degradation reaction rates. In a second-order reaction, higher degradation rate at a high concentration zone, contaminants degrade more effectively at the source than in a first-order reaction. It is conveyed that the pollutant transport is influenced by various parameters such as Peclet number, tortuosity, vegetation constraint, and dispersion time. For a specific water quality standard in wetlands, the maximal length and duration of the affected area for the common pollutant lead (Pb) is assessed and presented graphically; also, compared with a single zone. [ABSTRACT FROM AUTHOR]

Understanding hydrogen dispersion in a semi-confined space is crucial for the safe operation of hydrogen-related systems, such as hydrogen fuel cell vehicles. Analyzing hydrogen release and its subsequent dispersion can be effectively conducted using computational models, which necessitate experimental measurements for validation. For safety reasons, accidental scenarios are frequently replicated using helium as a hydrogen simulant in experiments, despite some concerns about the comparability of helium and hydrogen dispersions. Hence, this study conducts a comprehensive parametric numerical analysis of the similarities between hydrogen and helium dispersion when released in a semi-confined space. The model is based on the Macquarie Dispersion Chamber and the simulation results are first validated against the measurements. The study focuses on the impact of the leakage rate and ventilation velocity. Three release models were analysed: equal concentration (Method A), equal volumetric flow rate (Method B), and equal buoyancy (Method C). This study extends previous research on Method B, used for gas release in open spaces, to environments where flow-wall interactions become important. It also compares Methods A and C for a few scenarios, examining variations in concentration distribution, purge time, and activation time under different conditions. In the absence of ventilation, Method B effectively compares hydrogen and helium flow rates by accounting for volumetric flow rates, regardless of buoyancy effects. However, under increased ventilation velocities, Method A and Method C exhibit superior agreement across sensors, highlighting the necessity of choosing detection methods according to prevailing environmental conditions. [Display omitted] • A CFD model for gas release in semi-confined space equipped with ventilation is established. • Three release models are studied to investigate similarity between hydrogen and helium gas dispersion. • Purge time and activation time are analysed with the aim of safe hydrogen infrastructure development. • Influence on gas dispersion by various ventilation velocity and flow rate at leakage are analysed. [ABSTRACT FROM AUTHOR]

The stenosis builds up and its progression in the artery causes serious damages, which may lead to death. This research aims to investigate the non-Newtonian properties of the pulsatile blood flow through the multi-stenotic inclined artery. The effect of external body acceleration is considered, and blood is taken as Rabinowitsch fluid in this work. The mathematical model representing the proposed problem is transformed into a dimensionless form by applying the assumption for mild stenosis. The dimensionless mathematical equations are solved using the perturbation method. The solutions of mathematical equations are investigated graphically to analyze the impacts of various physical constraints. We find that strong non-Newtonian effects lead to an increase in flow velocity and wall shear stress. The stenosis's presence and progression in the artery reduces the flow velocity. The stenotic artery (diseased artery) is found to have less flow rate than the healthy artery. It is noted that the vertically held conduit effectively has a larger flow velocity and wall shear stress than the horizontal one. External body acceleration is noted to have an impact that raises velocity and wall shear stress. [ABSTRACT FROM AUTHOR]

Background: Brachycephalic dogs are overrepresented with ventricular enlargement. Cerebrospinal fluid (CSF) flow dynamics are not completely understood. MRI techniques have been used for the visualization of CSF dynamics including phase-contrast imaging. Objectives: This study aimed to determine a causality between CSF flow and ventriculomegaly or hydrocephalus and to compare CSF flow dynamics among dogs with ventriculomegaly, internal hydrocephalus, and physiologic ventricles. Animals: A total of 51 client-owned dogs were included in the study. Methods: Magnetic resonance imaging (MRI)-based FLASH sequences and phase-contrast images of the brain were obtained, and the ROI was placed at the level of the mesencephalic aqueduct. ECG monitoring was performed parallel to MRI acquisition. Evaluation of flow diagrams and processing of phase-contrast images were performed using commercially available software (Argus VA80A, Siemens AG Healthcare Sector, Erlangen, Germany). Dogs were divided into three groups: Group 1 consisted of brachycephalic dogs with ventriculomegaly (group 1A) or internal hydrocephalus (group 1B), group 2 consisted of brachycephalic dogs with normal ventricles, and group 3 consisted of meso- to dolichocephalic dogs with normal ventricles. Results: Group 1 had a higher median Vrost (4.32 cm/s; CI: 2.94–6.33 cm/s) and Vcaud (−6.1 cm/s, CI: 3.99–9.33 cm/s) than group 2 (Vrost: 1.99 cm/s; CI 1.43–2.78 cm/s; Vcaud: 2.91 cm/s, CI: 2.01–4.21 cm/s; p = 0.008; p = 0.03) and group 3 (Vrost:1.85 cm/s, CI: 1.31–2.60 cm/s; Vcaud − 2.46 cm/s, CI 1.68–3.58 cm/s; p = 0.01; p = 0.02). The median Volcaud of group 1 (−0.23 mL/min, CI: 0.13–0.42 mL/min) was higher than that of group 2 (−0.09 mL/min, CI: 0.05 mL/min and 0.15 mL/min) (p = 0.03). Groups 1A and 1B did not differ in Vcaud, Vrost, Volcaud, and Volrost. Group 1A and 1B showed a higher median Vrost (4.01 cm/s, CI: 2.30–7.05 cm/s; 5.94 cm/s, CI: 2.16–7.88 cm/s) than group 2 (1.85 cm/s, CI: 1.24–2.80 cm/s.) (p = 0.03; p = 0.004). Conclusion and clinical importance: Increased CSF flow velocities in rostral and caudal directions are present in dogs with ventriculomegaly and internal hydrocephalus compared to normal controls. [ABSTRACT FROM AUTHOR]

The hydrodynamic disturbance generated by the adult copepod Euchaeta antarctica during cruise swimming is quantified. Kinematic results are compared to previous results reported for different Euchaeta species. The results reveal a linear relationship between cruise speed and prosome length across Euchaeta species, indicating a size-proportional trend that is indicative of a complicated interaction of species size and environmental factors such as fluid temperature and viscosity. The detailed fluid flow measurements using the tomographic Particle Image Velocimetry (tomo-PIV) technique provide insight into copepod cruise propulsion during turning events in comparison to straight motions. During straight swimming, E. antarctica demonstrates streamlined flow patterns and reduced vorticity in the near-body fluid shear layer, which is beneficial for sustained motion and energy conservation. In contrast, turning maneuvers are characterized by maximum flow velocities reaching 1.5 times greater values than during straight cruising with increased flow field complexity and enhanced vorticity. The viscous dissipation rate generated in the flow disturbance is also greater during turning events, with the total dissipation rate reaching 3.5 - 3.8 × 10 - 8 W compared to 2.6 - 2.8 × 10 - 8 W during straight cruising. The flow disturbance also generates a hydrodynamic cue that prey may sense in order to avoid the predator E. antarctica. For the adult E. antarctica, the hydrodynamic cue extends to a volume that is 11–13 times larger than the copepod exoskeleton volume during the straight swimming motion and 22–25 times larger during the turn events. [ABSTRACT FROM AUTHOR]

The simple wickless structure and strong heat transfer potential of pulsating heat pipes (PHP) have prompted widespread interest in transferring heat from electronic devices. This work proposes a novel single-turn PHP with convergent and divergent shaped additional branches (ABs) (C-PHP and D-PHP) in the evaporator section, which could increase latent heat transfer in the evaporator by minimizing the saturation temperature and improving the unidirectional flow and thermal performance of PHP. Numerical simulations were performed using computational fluid dynamics (CFD) techniques to understand the thermo-hydrodynamics and properties of the proposed novel PHPs. This study provides the outcomes of novel PHPs and a comparison with the performance of traditional PHP (T-PHP) without AB and straight AB PHP (S-PHP). The results demonstrated that the startup time of novel C-PHP and D-PHP were improved by 32.6% and 22.4%, respectively, compared to the T-PHP, "stopovers" and "local flow reversals" are minimized by the use of AB. The average flow velocity of novel C-PHP and D-PHP was improved by 16% when compared to T-PHP and 11.4% compared to S-PHP, the directional component in C-PHP is substantially stronger than S-PHP and D-PHP. [ABSTRACT FROM AUTHOR]

Objective Methods Results Interpretation Brief exposure to intermittent hypoxia has been shown to potentially induce protective effects in the body. Animal studies suggest that intermittent hypoxia could increase cerebral blood flow and confer resistance to subsequent hypoxic–ischemic injury, yet clinical investigations are limited. This study aimed to evaluate the impact of a moderate short‐term intermittent hypoxia protocol on cerebral blood flow and cognitive performance.Subjects who met the inclusion criteria were recruited to this study and randomized into the intermittent hypoxia group or the control group, which receives intermittent hypoxia training and sham‐intermittent hypoxia training, respectively. Cerebral hemodynamics, cognitive performance, cerebral perfusion pressure, and oxygen saturation were assessed before and after the intervention.A total of 100 healthy participants were included in this study. Compared to the control group, the intermittent hypoxia group exhibited higher peak systolic blood flow velocity (108.64 ± 22.53 vs. 100.21 ± 19.06, p = 0.049) and cerebrovascular conduction index (0.74 ± 0.17 vs. 0.66 ± 0.21, p = 0.027), and lower cerebrovascular resistance index (1.41 ± 0.29 vs. 1.54 ± 0.36, p = 0.044) following intermittent hypoxia training. Additionally, within‐group comparisons revealed that intermittent hypoxia training led to increased cerebral blood flow velocity, elevated cerebrovascular conductance index, and decreased cerebrovascular resistance index (p < 0.05). Other indicators including cognitive function, cerebral perfusion pressure, and oxygen saturation did not exhibit significant differences between groups.These findings revealed that intermittent hypoxia may represent a safe and effective strategy for improving cerebral blood flow. [ABSTRACT FROM AUTHOR]

Background Methods Results Conclusions Antihypertensives (AHD) can influence cerebral autoregulation (CA) and attenuate hypertrophic concentric remodelling of arterioles. The aim of this study was to examine the associations between AHD, CA and structural and functional properties of cerebral arteries.In this observational, cross‐sectional study 115 volunteers were divided in group 1 (non‐hypertensive) [n = 30]; group 2 (hypertensive with systolic blood pressure [SBP] < 140 and diastolic blood pressure [DBP] < 90 mmHg) [n = 54]; group 3 (hypertensive with SBP ≥ 140 or DBP ≥ 90 mmHg) [n = 31] and simultaneous measurements of systemic blood pressure (BP) and middle cerebral artery blood flow velocity (CBFV) were obtained from digital plethysmography and transcranial Doppler. Beat‐to‐beat, critical closing pressure (CrCP), resistance‐area product (RAP) and autoregulation index (ARI) values were extracted by linear regression analysis of instantaneous BP and CBFV waveforms using computerised analysis. Pulsatility index (PI) was calculated and CO2 reactivity was assessed by the breath‐holding test.Despite their higher RAP (1.7 [±0.7], p < 0.001) compared to groups 1 and 2, uncontrolled hypertensive using diuretics (p = 0.047) and α2‐agonists (p = 0.009) had significantly lower PI. Impaired CO2 reactivity was common between the two hypertensive groups (p = 0.008), however ARI, CrCP and CBFV did not differ between them and non‐hypertensive individuals and also did not correlate with any AHD used.Unlike the RAP, PI does not seem to reflect the real cerebrovascular resistence resulting from chronic arterial remodelling. Despite impaired CO2 reactivity, hypertensive have arterial tonus and CA comparable to non‐hypertensive. Experimental studies involving an untreated hypertensive control group are required to robustly make definitive conclusions about these questions. [ABSTRACT FROM AUTHOR]

Long-term human spaceflight can lead to cardiovascular deconditioning, but little is known about how weightlessness affects microcirculation. In this study, we examined how the retinal microvessels and cerebrovascular regulation of 19 healthy male participants responded to long-term head-down bedrest (HDBR), an earth-based analog for weightlessness. In addition, we examined whether an anti-inflammatory/antioxidant cocktail could prevent the vascular changes caused by HDBR. In all study participants, we found a decrease in retinal arteriolar diameter by HDBR day 8 and an increase in retinal venular diameter by HDBR day 16. Concurrently, blood pressure at the level of the middle cerebral artery and the cerebrovascular resistance index were higher during HDBR, while cerebral blood flow velocity was lower. None of these changes were reversed in participants receiving the anti-inflammatory/antioxidant cocktail, indicating that this cocktail was insufficient to restore the microvascular and cerebral blood flow changes induced by HDBR. [ABSTRACT FROM AUTHOR]

Background: This research aimed to ascertain independent risk factors and the diagnostic value of vascular parameters in differentiating posterior circulation ischemic isolated vertigo (PCI-IV) from vestibular peripheral vertigo (VPV). Methods: This study involved 247 patients with acute-onset vertigo, categorized into two groups: PCI-IV and VPV. Multivariate logistic regression was conducted to pinpoint independent risk factors for PCI-IV. Results: The duration of vertigo, particularly episodes lasting more than a few hours, was a significant predictor of PCI-IV (OR = 2.183, p < 0.001). The presence of diabetes mellitus (OR = 1.746, p = 0.008) and hypertension (OR = 2.291, p = 0.004) also notably increased the likelihood of PCI-IV. Hemodynamic measurements such as the inner diameter and average blood flow velocity (Vmean) of the vertebral artery, as well as the resistive index (RI), were identified as significant predictive factors (p ≤ 0.033). The ROC analysis demonstrated the vertebral artery RI had the highest diagnostic accuracy with an area under the curve (AUC) of 0.78, indicating an optimal balance between sensitivity and specificity. Conclusion: Clinical features such as the duration of vertigo, diabetes mellitus, and hypertension, along with vascular hemodynamics, are crucial in assessing the risk of PCI-IV. The RI in the vertebral artery emerged as a particularly potent diagnostic parameter. These findings advocate a multifaceted diagnostic approach, combining clinical and vascular parameters for the effective identification and management of PCI-IV. [ABSTRACT FROM AUTHOR]

Background: Spectrum of chronic orthostatic intolerance without orthostatic hypotension includes postural tachycardia syndrome (POTS), with orthostatic tachycardia and hypocapnic cerebral hypoperfusion (HYCH), without orthostatic tachycardia. This study compared autonomic, cerebrovascular, and neuropathic features of POTS and HYCH. Methods: This retrospective study evaluated patients with orthostatic intolerance referred for autonomic testing. Analyzed data included surveys (Survey of Autonomic Symptoms, Compass-31, Neuropathy Total Symptom Score-6, Central Sensitization Inventory) and autonomic tests (Valsalva maneuver, deep breathing, sudomotor and tilt tests), cerebrovascular (cerebral blood flow velocity (CBFv) monitoring in the middle cerebral artery), respiratory (capnography), neuropathic (skin biopsies for assessment of small fiber neuropathy) and invasive cardiopulmonary exercise testing (iCPET). Results: A total of 127 HYCH, 125 POTS, and 42 healthy controls were analyzed. Compared HYCH to POTS patients, there was no difference in the duration of symptoms, the prevalence of younger women, comorbidities, sensory and autonomic complaints, central sensitization syndrome, supine/standing norepinephrine levels, inflammatory markers and medical therapy except for gastrointestinal medication. Autonomic testing showed widespread but similar abnormalities in POTS and HYCH that included: reduced orthostatic CBFv and end-tidal CO2, preload failure (assessed in 16/19 POTS/HYCH), mild autonomic failure, and frequent small fiber neuropathy. Conclusion: HYCH and POTS are syndromes of orthostatic intolerance with cerebral hypoperfusion associated with reduced orthostatic cerebral blood flow, hypocapnia, mild autonomic failure and small fiber neuropathy of a similar degree and distribution; except for tachycardia in POTS. Similarities in peripheral domain abnormalities that affect heart rate suggest that orthostatic tachycardia in POTS is driven by the central nervous system overcompensation of orthostatic challenge. These findings provide additional evidence that HYCH and POTS represent a spectrum of the same disorder. Reduced orthostatic cerebral blood flow is a key unifying feature of HYCH and POTS. [ABSTRACT FROM AUTHOR]

This paper reports on preliminary observations of an investigation of flows associated with models that mimic serrations on the leading edge of barn owl feathers. The objective was to use particle image velocimetry measurements to determine the capacity of singular and multiple curved (three-dimensional) serration models to modify the noise-reducing indicators of a narrow-channeled flow past a cylinder. Four models were tested: 3 singular serration models of respective angles of inclination, α = 24°, 27.5° and 31°, and a model consisting of an array of 3 serrations of α = 24°, 27.5° and 31°. Each case was subjected to flow of Reynolds number (based on the serration height and maximum velocity of the flow) of ∼2,000, simulating the flow regime of local flow around barbs of real barn owl flights. A planar particle image velocimetry technique was used to capture the midspan plane velocities to determine the effects of each model. The results show that using singular serration models of inclination angles than 30° may lead to disorganized spatial structures and enhanced turbulence levels. On the other hand, an array of only 3 curved serrations of different geometries can modify the spatial flow structure into a well-ordered one, resulting in a 50% reduction in turbulence intensities. These initial results suggest that under complex flow conditions, the insertion of single and multiple curved serrations can lead to significant flow changes that may result in potential noise modifications. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the entropy production characteristics of two non-miscible fluids in an inclined porous channel with temperature-dependent thermal conductivity and viscosity. The porous region of the channel is divided in two regions. In region-1 and region-2, the Couple stress and Newtonian fluid take place due to constant pressure gradient, respectively, under the influence of a uniform magnetic field. Here, the Darcy–Brinkman model is used for the flow of immiscible fluid through the porous media. In this work, we used a semi-analytical method named as homotopy analysis method (HAM) to solve the coupled nonlinear ordinary differential equations. The goal of the considered problem is to examine the consequences of a variety of thermophysical parameters, including Hartmann number, varying viscosity parameter, varying thermal conductivity parameters, and Grashof number on the characteristics of entropy generation, Bejan number distribution, thermal behavior and flow characteristics of non-miscible couple stress and Newtonian fluid passing through a porous channel. The novel aspect of this study is the formation of entropy and Bejan number as a result of non-miscible Newtonian and couple stress fluids with varying thermal conductivity and viscosity in porous media. In terms of rheological investigation, a semi-analytical simulation for changeable thermal and flow properties in an immiscible Newtonian and couple stress fluid via an inclined porous channel is a brand-new concept, and the behaviors of such flows have not been examined yet. From this study, it is concluded that on raising the variable thermal conductivity, Hartmann number and the permeability of the porous medium, the flow velocity, thermal characteristics and entropy generation number decrease. The authors also come to the significant conclusion that non-miscible Newtonian and couple stress fluids have larger entropy production numbers, flow velocities, and temperature profiles for higher values of Grashof number, variable viscosity parameter, and couple stress parameter. The findings of this work have also been graphically validated through the previously established work. The results of the present analysis can be used in petroleum industry, lubrication theory, etc. [ABSTRACT FROM AUTHOR]

This study presents an investigation on the generalized Couette flow of two immiscible Newtonian fluids in an anisotropic porous medium. The flow occurs between two parallel plates, driven by the combined effects of an axial pressure gradient and the movement of the upper plate. The region between the plates is filled with an anisotropic porous medium characterized by directional permeability. An exact solution is derived for the proposed problem by considering appropriate boundary and interface conditions. The slip condition is employed at the lower plate of the channel which has a significant role in the flow mechanics of fluids flowing through porous medium. The effects of directional permeability on the flow of immiscible fluids are explored, and specific cases are presented. This study reveals a significant influence of directional permeability on the flow velocity of both fluids. Furthermore, quantitative conclusions are drawn regarding the shear stress at the lower and upper wall of the channel, with implications for the anisotropic nature of blood arteries. The findings contribute to a deeper understanding of fluid flow in anisotropic porous media and have potential applications in various engineering domains. [ABSTRACT FROM AUTHOR]

Continuous flow magnetophoresis represents a common technique for actively separating particles within a fluid. For separation systems design, accurately predicting particle behaviour helps to characterise system performance, typically measured by the separation efficiency (SE). While finite element method (FEM) simulations offer high accuracy, they demand extensive computational resources. Alternatively, results can be achieved more quickly with simplified numerical models that use analytical descriptions of fluid flow, magnetic fields, and particle movement. In this research, we model a millifluidic system that separates magnetic particles using magnetophoresis. Therefore, we (1) develop a simple numerical model that can simulate continuous flow magnetophoresis for rectangular channels in two and three dimensions, (2) introduce a novel and simple approach to calculate the SE, and (3) quantify the effects of model assumptions in flow profile and dimensions on SE. Our method for estimating SE considers particle flux variation across the channel's cross-section due to the flow profile. The results are compared to an FEM model developed in COMSOL. The obtained three-dimensional simulation model computes results in seconds, around 180 times faster than the FEM approach, while deviating less than 2% from the FEM results. A comparison of the different two-dimensional and three-dimensional models underscores the significant influence of the flow profile and the SE calculation method on the result. The two dimensional models generally overestimate the SE of up to 15% due to their lower peak flow velocity. However, using a constant flow velocity leads to good agreement for high SE due to the overlap of differences in flow profile and SE calculation. [ABSTRACT FROM AUTHOR]

Modulating inflammation is crucial for repairing vascular injury. Phagocytosis of apoptotic cells represents an effective mechanism for attenuating inflammation and improving regeneration during natural healing. However, strategies for repairing vascular injuries using biomaterials derived from apoptotic cells are still undeveloped. Herein, apoptotic body‐mimetic nanovesicles (ApoNVs) derived from rat adipose‐derived mesenchymal stem cells (rASCs) are prepared using a one‐step extrusion method. ApoNVs inherit the unique anti‐inflammatory and pro‐regenerative properties of the parental apoptotic rASCs, as evidenced by enhanced M2 polarization of macrophages and promoted endothelial cell proliferation and migration following treatment with ApoNVs. Moreover, ApoNVs enhance the contractile phenotype of vascular smooth muscle cells through the mediation of ApoNVs‐induced repolarized macrophages. After engineering ApoNVs with P‐selectin binding peptide (ApoNVs‐PBP), their ability to target injured artery increased nearly sevenfold compared to unmodified ApoNVs. In a rat wire‐mediated femoral artery injury model, ApoNVs‐PBP effectively suppress inflammation and significantly reduce blood flow velocity and neointimal hyperplasia at the injury site. ApoNVs exhibit similar therapeutic effects, though to a lesser extent. This study provides strong evidence validating the targeted delivery of ApoNVs as an innovative approach for repairing vascular injury and highlights their potential in treating other inflammatory diseases. [ABSTRACT FROM AUTHOR]

The article focuses on adapting generalized depth preference and flow velocity characteristics from Brown trout (Salmo trutta morpha fario) to the Minnow (Phoxinus phoxinus). The results obtained were used to model habitat suitability with 1D and 2D models. Since 1995, research on assessing aquatic habitat quality has been ongoing on 77 mountain streams in Slovakia. This assessment employs a System of Environmental Flow Analysis (SEFA), which is based on the Instream Flow Incremental Methodology (IFIM). In most sections, Brown trout occurred in representative numbers. Brown trout habitat preferences were derived and generalized, and represented by suitability curves. Minnows were present in sufficient numbers for the derivation of suitability curves only on some streams, making direct generalization from the measured data unrepresentative. The measurement results showed that Minnow has similar depth and flow rate preferences to Brown trout. Therefore, it can be assumed that it is possible to adapt the generalised suitability curves from Brown trout to Minnow. This expansion enabled us to broaden the assessment of habitat quality using the SEFA model to mountain streams that are dominated by Minnows and where there is insufficient Brown trout presence. Verification of parameter adaptation from Brown trout to Minnow was conducted in 11 sections of mountain streams. We discuss the performance of habitat quality modeling, concerning the fundamental hydraulic characteristics of streams, using both 1D and 2D models. The results of the 2D modeling are presented for a sub-mountain stream. [ABSTRACT FROM AUTHOR]

Objective Design Setting Animals Interventions Measurements and Main Results Conclusions To evaluate the changes in flow velocities of the middle cerebral artery before and after a carotid compression maneuver using transcranial color‐coded duplex sonography (TCCD) in healthy anesthetized dogs under mechanical ventilation.Prospective study.University teaching hospital.Eleven healthy adult dogs.A 5‐second carotid occlusion maneuver was performed to evaluate cerebral autoregulation (CA).After 10 minutes of stable anesthesia, the middle cerebral artery was evaluated by TCCD. Dogs were positioned in sternal recumbency with the head raised to the level of the phlebostatic axis. The systolic peak velocity (Vp) was measured using pulsed Doppler mode. CA was evaluated through the transient hyperemia test (THT), which assesses changes in the Vp after a 5‐second transient compression of the ipsilateral common carotid artery and is expressed as the ratio between the Vp flow before and after carotid compression. The Vp before and after carotid occlusion was compared using the Wilcoxon signed‐rank test. The median Vp of the middle cerebral artery after the carotid compression maneuver was significantly higher than the median Vp before compression (median [interquartile range, IQR]: 47.7 cm/s [34.3] vs 64.1 cm/s [24.4]; P = 0.003). The median THT obtained was 1.20 (IQR: 0.37).The current study demonstrated a significant increase in the Vp of the middle cerebral artery after a 5‐second temporary occlusion of the ipsilateral carotid artery in healthy anesthetized dogs under mechanical ventilation. These findings suggest that the noninvasive TCCD methodology could be valuable for assessing CA in dogs. Additional studies using this technique in neurocritical animals are required to confirm its usefulness. [ABSTRACT FROM AUTHOR]

The high‐rate electrochemical dissolution of copper in nitrate electrolytes is investigated primarily via polarization curves, while varying parameters such as the electrolyte flow velocity, the electrolyte resistance, the anode geometry, and the temperature. This study focuses on the re‐rise in current at high voltages after the limiting current plateau. As a result of the studies, a change in the complexation mechanism from hydration to "solvo‐nitration" is proposed, which requires an additional potential drop within the electrochemical double layer. [ABSTRACT FROM AUTHOR]

A diesel engine is the most energy-efficient powerplant in agricultural machinery. However, the performance of cold start has been limited to the diesel fuel viscosity in the low-temperature environment. Fluidity deterioration has also inhibited diesel spray atomization and evaporation, leading to the low reliability of diesel engines. In this study, the backlight test was conducted to compare the variation in the spray macrostructure of high and low-temperature diesel under different working conditions. The digital image processing of the spray images was then carried out using MATLAB to obtain the macroscopic characteristic parameters of the spray. The test results showed that the much more outstanding impact on the injection volume was obtained in the diameter of the spray hole 0.12 mm with the various injection pressures at diesel temperature. The continuous viscous force slowed down the flow velocity of the fluid layer near the wall and then suppressed the diesel emission. Once the diesel temperature was lower than 0 ℃, the diesel temperature was reduced by the amount of injection. The diesel temperature decreased to enhance the viscous force among droplets at high injection pressure. The continuous ejection of diesel was then promoted under the action of kinetic energy and inertial force. The fuel injection amount increased with the decrease in diesel temperature. When the injection pressure was 75 MPa, the diesel temperature dropped to -20 ℃, compared with 38 ℃ diesel injection quantity increased by nearly 23.87 %. The diesel temperature decreased under small pore size, leading to the increase of viscous force among droplets. There was an increase in the droplet size and the greater momentum of droplets. Thus, the radial development trend of diesel spray was weakened to enhance the axial movement. Furthermore, the spray penetration increased with the decrease of diesel temperature, whereas, the spray cone angle decreased. The diesel spray penetration increased by 39.89 mm at 0.70 ms when the diesel temperature decreased from 38 ℃ to -20 ℃. When the nozzle diameter was 0.28 mm, the injection pressure was less than 75 MPa, and the injection quantity decreased with the decrease of diesel temperature. More momentum of diesel was consumed to overcome the greater internal friction under the same injection pressure. The farthest distance to reach was weakened. Diesel temperature was reduced to decrease the spray penetration and spray cone angle. When the injection pressure was 75 MPa, the diesel spray penetration at -20 ℃ at 0.70 ms was 30.86 mm shorter than that at 38 ℃. The spray penetration of -20 ℃ diesel decreased with the increasing nozzle diameter at the same injection pressure, whereas, the spray cone angle increased. Secondly, there was a more prominent influence of diesel temperature on the macroscopic characteristics of the spray with the increase in injection pressure. The higher the injection pressure was, the more outstanding the shortening trend of spray penetration caused by the decrease in diesel temperature was. Therefore, the injection pressure and nozzle diameter can be expected to improve for better evaporation and gasification of diesel liquid phase spray at low temperatures. [ABSTRACT FROM AUTHOR]