Changes In Flow Velocity Research Articles

Morphohydraulic of a dam-impacted large river: The São Francisco River, Brazil

Many studies have highlighted dam impacts in the reduction of the transmission of nutrient loads and suspended sediments downstream, increasing coastal erosion (sediment budget) and water residence time, beyond modifying the channel planform on a reach scale. However, the morphohydraulic changes, which are induced by flow regulation, have been little explored. This study has sought to analyze temporal changes in the at-a-station hydraulic geometry from 9 cross-sections along the São Francisco River, comparing the pre and post-dam periods. In addition to that, it was also sought to compare our results with other tropical river systems and assess the relationships of morphohydraulic parameters with channel patterns and functional trends. We have used field data collected by the National Water Agency and the Geological Survey of Brazil covering the middle, lower-middle, and lower courses of the São Francisco River. Potential functions were extracted using the least squares fit method. We have applied the Mann-Whitney non-parametric statistical test to assess any dataset changes. Finally, we have analyzed the data through the ternary diagram. Our results have demonstrated that the São Francisco River has high bank stability and variations in flow are mainly accommodated by changes both in depth and flow velocity. We found changes in the sensitivity of width, depth, and velocity in the post-dam period that imply high mobility of the cross-sections in the ternary diagram. Changes in land use patterns are potentially associated with these observed changes. Despite the São Francisco banks being stable in the analyzed cross-sections, the sensitivity of the channel width increased in the post-dam period. Differences were observed between the response patterns in the post-dam period in the physiographic provinces of the São Francisco River. However, the increase in width sensitivity predominates, with few exceptions. Hydraulic geometry analyses have proved to be essential for the characterization of the functional dynamics of river systems and allowing inferences about sediment transport conditions, flow stage, and channel stability.

Impairment of cerebral CO2 dynamic vasoreactivity in MCI & AD patients: a multi‐center study of cerebral flow regulation

AbstractBackgroundAlzheimer’s Disease Centers in Los Angeles (USC), Dallas (UT‐SWMC) and Kansas City (KUMC) have joined together to study the regulation of cerebral perfusion through analysis of spontaneous time‐series data using a modeling methodology that previously yielded indications of reduced CO2 dynamic vasomotor reactivity (DVR) in amnestic MCI patients. We report initial results from this ongoing multi‐center study that confirm those preliminary findings and, furthermore, elucidate the effects of slow‐paced breathing.MethodFive‐minute spontaneous changes in arterial blood pressure (ABP), end‐tidal CO2 (etCO2) and cerebral blood flow velocity (CBFV) in middle cerebral arteries were obtained before and after 5‐min session of slow‐paced breathing (8 breaths/minute). Using data from 25 MCI patients, 7 AD patients and 45 age‐matched cognitively normal controls (NC), we obtained predictive models of the dynamic effects of ABP and etCO2 (proxy for blood CO2) upon CBFV via our kernel‐based modeling methodology. These predictive models were used to compute indices (physio‐markers) that quantify the DVR in each participant, as time‐average of the model‐predicted CBFV response to unit‐step change of etCO2 over the first 30 seconds.ResultThe obtained DVR indices were significantly different for the 32 patients (MCI and AD lumped together due to small number of AD) vs. 45 age‐matched controls (p= 0.0099). Notably, the delineation between patients and controls improved (p= 0.0011) after a 5‐min session of slow‐paced breathing. Figure 1 shows the average model‐predicted CBFV response to unit‐step change of etCO2 for 32 MCI/AD patients (red line) and 45 controls (blue line) before and after the 5‐min paced‐breathing session. Note the negative average steady‐state CBFV response of the patients (red) that indicates polarity reversal of the normal CO2 vasomotor reactivity (blue). Better delineation between patients and controls is achieved (p= 2x10‐5) when the DVR indices from the two sessions, before and after slow‐paced breathing, were averaged (see histograms in Figure 2).ConclusionSignificantly lower DVR indices under resting spontaneous conditions were observed in 32 MCI/AD patients relative to 45 age‐matched controls. This reduction is detected more reliably after 5‐min of slow‐paced breathing. Averaging of the DVR indices obtained before and after slow‐paced breathing improved further this delineation (p= 2x10‐5).

IMPACT OF RELATIVE BLOOD FLOW VELOCITY HYPERPERFUSION DURING CARDIAC SURGERY WITH CARDIOPULMONARY BYPASS TO DELAYED NEUROCOGNITIVE RECOVERY

<h3>Objective</h3> Inflammation, neuronal, vascular damage/embolism, cerebral autoregulation and perfusion, oxygen delivery are known as etiological factors of delayed neurocognitive recovery (dNCR). Many researchers have identified that neuropsychological complications emerge from insufficient cerebral perfusion. Relative cerebral hyperperfusion also disrupts cerebral autoregulation and might play a significant role in dNCR development. The aim of this study was to determine the influence of increased a. cerebri media (ACM) blood flow velocity (BFV) during cardiac surgery with cardiopulmonary bypass (CPB) on delayed neurocognitive recovery. <h3>Design and Method</h3> This prospective - case control study included patients undergoing elective coronary artery bypass grafting (CABG) or/and valve surgery with CPB. For cognitive evaluation 110 patients completed ACE-III. To determine mild cognitive dysfunction, cut - off 88 was chosen. Mean BFV was monitored with transcranial Doppler ultrasonography (TCD) and performed before surgery and at the beginning, middle and ending of CPB. The average of three CPB measurements was used for calculation. Preoperative BFV was converted to 100% and used as a baseline. The percentage change of cerebral blood flow velocity during CPB was calculated from baseline. Patients with decreased blood flow velocity were included for further investigation. <h3>Results</h3> 101 patients were examined, 67 (69,1%) men and 29 (29,9%) women, age 67.9 (SD 9.2) Increased percentage of BFV was determined for 40 (39.60%) patients. Patients' demographic data are shown in Table 1. Percentage change of BFV was 105.60 % (min 100.21; max 148.02) in the non-dNCR group and 132.29 % (min 101.34; max 150.26) in the dNCR group, p=0.033 (Figure Nr. 1). During the study, we assessed the relationship between patients age and ACE-III test results together with ACM BFV. Spearman correlation analysis revealed that age had negative moderate correlation with ACE-III test results after surgery (Spearman r -0.597, p< 0.01) and negative moderate correlation with ACM BFV during CPB (Sprearman r -0 .529, p <0.01) (Figure 2 and 3). <h3>Conclusions</h3> Patients that develop dNCR were significantly older and had a lower baseline BFV. Results suggest that the main cause of hyperperfusion during CPB is age related lower BFV before surgery. Elderly patients are more sensitive to relative hyperperfusion during CPB, therefore dNCR was diagnosed more often in patients with higher percentage change of BFV.

Simulation and experimental study of Taylor cone and jet evolution process parameters in electrohydrodynamics

In melt electrospinning, accurate control of jet evolution and Taylor cone process parameters helps to control the final fiber properties. High-speed photography was employed to observe the jet's formation process and the Taylor cone's morphology. A multi-physics model of nonisothermal heat transfer was used to predict the fluid flow direction and velocity change. In addition, we investigated the relationships between the process parameters of the Taylor cone and the diameter of melt electrospun fiber. The results show an excellent linear relationship between the process parameters (cone angle, curvature, and Taylor cone height) and fiber diameter. According to the simulation results, the axial fluid flow keeps the maximum and accelerates continuously until the collector captures it. In addition, with the increase of voltage, the fiber strength is lower, and the crystallinity is improved. This work analyzes diameter and process parameters and offers a fresh perspective on electrostatic-fluid interaction and a method to forecast fiber diameter.

Comparative evaluation of the effectiveness of phlebotonic gels

Introduction. Varicose veins are a common disease with a chronic course and a high risk of complications and cosmetic defects. Venotonic drugs are widely used in conservative treatment of varicose veins.Aim. To study the comparative efficacy of venotonic drugs for local application in experimental conditions.Materials and Methods. Varicose veins were modeled in Wistar rats by partial stricture of the deep femoral vein. The studied drugs were applied in the course of 14 days from the operation. The assessed parameters were the change of local blood flow velocity in the skin in the dynamics and the degree of vascular permeability. The rate of local blood flow was assessed by Doppler ultrasound. Changes in vascular permeability were studied by the degree of extravasation of Evans blue dye in the Miles test. The results were processed using the methods of variation statistics.Results. The study showed that under the conditions of experimental chronic venous insufficiency, a course of application of all the analyzed drugs resulted in an increase in the rate of local blood flow in the skin and a decrease in the degree of vascular permeability. It was noted that application of the investigated gel based on escin, heparin and essential phospholipids to the skin of animals resulted in reliably (p &lt; 0,05) lower indices of vascular permeability in comparison with the rats which received a course therapy with the heparin-containing gel; combined cosmetic agent as well as the gel based on troxerutin, heparin and dexpanthenol.Discussion. The results obtained testify that application of external dosage forms of combined venotonic drugs promotes the regression of chronic venous insufficiency manifestations. Maximum evident effect was registered while applying the studied drug, that can be related to its complex composition including essential phospholipids, heparin and aescin. It is known that aescin is a phlebotonic with a high degree of percutaneous absorption, the effect of which is significantly potentiated by the phospholipid component.Conclusions. The application of the combined product based on heparin, aescin and essential phospholipids provided an optimum rate of onset of pharmacological effect compared to the other analysed compositions.

Evaluation of the changes in middle cerebral artery flow velocity related to different positions of patients during posterior fossa surgery.

This is a prospective observational study to evaluate the changes in middle cerebral artery flow velocities and cerebral perfusion pressure in the various positions used for posterior cranial fossa surgery and to correlate these changes with postoperative recovery characteristics and complications. Sixty patients were included in the study - 33 patients with CPA tumors were placed in the supine with head tilt position and the rest 27 with tumors in other locations of posterior fossa were placed in the prone position. The primary aim was to study the changes in middle cerebral artery blood flow velocity related to various positions of the patients used during posterior fossa surgery. The secondary aim was to compare the changes in pulsatility index, resistance index, and effective cerebral perfusion pressure in different position and to correlate these findings with postoperative recovery and the complications associated with these positions. The systolic and mean flow velocities were higher in the supine with head tilt group than the prone group after positioning and post repositioning, but these values were within normal limits, and the changes with positioning from baseline were comparable between the groups. Furthermore, these changes did not affect the effective cerebral perfusion pressure or the outcomes of the patients. The current results do not determine whether the supine with head tilt position is better than the prone position during posterior fossa surgery.

Pilot study on the effect of grape seed proanthocyanidin extract on inferior vene cava blood flow in patients with chronic venous insufficiency using 4D flow MRI.

Four-dimensional (4D) flow magnetic resonance imaging (MRI) was used to objectively assess changes in blood flow velocity in patients with chronic venous insufficiency (CVI) who underwent stocking treatment alone and stocking combined with Grape seed proanthocyanidin extract (GSPE) treatment. Patients diagnosed with CVI were recruited from August 31, 2018 to December 31, 2020. A total of 23 participants were selected, with 10 and 13 patients in the stocking treatment and stocking + GSPE treatment groups, respectively. The blood flow velocity (Th-plane peak and average velocities) was calculated using 4D flow MRI. A paired t test was used to evaluate the differences in blood flow velocity before and after treatment. In the stocking treatment group, The Th-Plane peak velocity increased by 2.48 ± 5.05 cm/s after treatment (P = .16). In the stocking + GSPE treatment group, the Th-Plane peak velocity increased by 4.85 ± 5.57 cm/s after treatment (P < .001). The blood flow velocity on 4D flow MRI was significantly increased in participants who underwent GSPE, highlighting the potential of GSPE for CVI treatment.

Cardiorespiratory effects of different intraabdominal pressures in sheep: An experimental study.

Increased intraabdominal pressure (IAP) during laparoscopy can reduce venous return, but changes in respiratory system mechanics and their effect in left cardiac function are not well documented. This study evaluated the effects of different IAPs on respiratory mechanics and cardiac function in 10 healthy nonpregnant adult Santa Ines ewes randomly submitted to a crossover study using different IAPs: 0 mm Hg (G1), 10 mm Hg (G2), 12 mmHg (G3), and 15 mmHg (G4). Animals were anesthetized and mechanically ventilated (VT =15 ml/kg; positive end-expiratory pressure=3 cmH2 O; FiO2 =1.0). Pneumoperitoneum was induced by Hasson's trocar cannula. Variables were measured at INITIAL (IAP, 0 mmHg) and FINAL time points for each IAP after 1 h. At FINAL, driving airway pressure (ΔP,RS ), and percentage fraction of dead space (Vd/Vt) were higher in G3 and G4 than G1 (p=0.002, difference in means [MD] 4.60, 95% CI: 7.91-1.28, and p < 0.001, MD 5.4, 95% CI: 8.7-2.0; p=0.016, MD -9.5, 95% CI: -17.9 to -1.2; and p=0.027, MD -8.7, 95% CI: -17.1 to -0.4). The ejection fraction and fractional shortening were lower in G3 (p=0.039, MD -11.38, 95% CI: -0.07--22.68; p=0.015, MD -13.05, 95% CI: -1.74--24.36) and G4 (p=0.039, MD -9.94, 95% CI: -0.07 to -19.80; p=0.015, MD -11.43, 95%CI: -1.57 to -21.30, respectively) than G2. In G3, the maximum pulmonary flow velocity correlated negatively with ΔP,RS (r=-0.740; p=0.018), and Vd/Vt correlated positively with ΔP,RS (r=0.738, p=0.046). At IAP of 12 and 15 mm Hg impaired respiratory system mechanics, reduced left cardiac function and no change in maximum pulmonary artery flow velocity were detected. Therefore, respiratory mechanics should be monitored as an interplay to reduce left cardiac function.

Recovery of heavy medium in coal washing plant using a flat plate magnetic separator and optimization of flow and magnetic fields

Heavy medium coal washing technique can achieve deep coal desulfurization and ash reduction. It is an important approach that can ensure clean and efficient utilization of coal. Heavy medium coal washing technique is affected by the efficient and high-quality recovery of heavy medium. While, it has the poor recovery due to the finer particle size and weaker magnetic property using the drum magnetic separator. In this study, the recovery of heavy medium was performed using a flat magnetic separator based on a plane extrusion magnetic system. The effect flow field and magnetic field on the recovery of the heavy medium were theoretically discussed, and the mechanism was clarified. The main results demonstrated that the plane extrusion magnetic system had a high magnetic field strength with B > 0.5 T, and the magnetic field distance was greater than 30 mm with B > 0.2 T. Additionally, the leakage of magnetic field lines was less regardless of the position of the magnetic poles. The magnetic system was suitable for plate installation. A fluid domain height changes from 40 cm to 60 cm during the recovery cycle had a significant effect on the magnetic field strength, and an increase in the fluid domain height extended the motion trajectory of the magnetic particles. A flow velocity changes from 1.2 m/s to 2.0 m/s directly affected the competitive forces intensity. However, the competitive intensity was significantly less than that of the magnetic force, and an increase in the flow field velocity slightly affected the motion trajectory of magnetic particles. The effect of the magnetic particle concentration on the motion trajectory of magnetic particles was unclear due to the stable magnetic properties of the heavy medium. The theoretical and experimental analysis confirmed that the thin flow field film separation space of the flat plate magnetic separator and the magnetic field characteristic of the plane extrusion magnetic system, could be beneficial to the separation of finer particle size and weaking magnetic susceptibility. Additionally, the counterbalance relationship between the magnetic and competitive forces fulfilled the requirements of the high-efficiency magnetic separation of the heavy medium.

Relationships between the Clinical Test Results and Neurophysiological Findings in Patients with Thoracic Outlet Syndrome.

A thoracic outlet syndrome (TOS) is the type of brachial plexus disorder most difficult to objectively assess using a clinical examination and differential diagnosis. Its symptoms can be frequently misdiagnosed, especially among others with cervical disc-root conflicts, plexopathies, and peripheral neuropathies. In this study, we aim to identify the correlations between positive Doppler ultrasonography results indicating pathological changes in the subclavian flow velocity, clinical tests, and chosen clinical neurophysiology recordings as proposed alternative or supplementary diagnostic tools for evaluating TOS patients. Sixty TOS patients with positive Doppler ultrasonography and Roos test results and sixty healthy people as a control group were bilaterally examined, and the results were compared. Pain intensity was assessed using a visual analogue scale (VAS). Sensory perceptions within C4–C8 dermatomes were assessed with Von Frey filament (FvF) tests. The activity of motor units in the proximal and distal muscles of the upper extremities was evaluated using surface electromyography (sEMG) during maximal contractions before and after a provocative raised hands test (RHT). An electroneurography (ENG) was used to evaluate the transmission of nerve impulses peripherally. Motor evoked potential (MEP) recordings, induced by the over-vertebral magnetic stimulation of the C5–C7 neuromeres, were used to examine motor transmissions from the cervical motor centres to the upper extremities muscles. The results revealed a relationship between positive Doppler test scores and pathological changes in the subclavian flow velocity through the results of the following diagnostic tools: a VAS score of 1.9 was detected on average, superficial sensory perception abnormalities were found in the innervation areas of the ulnar nerves detected by FvF tests, a decrease in the amplitudes of sEMG recordings was seen in distal rather than proximal muscles (especially following the RHT), a decrease in the motor and sensory peripheral transmissions of nerve impulses in the median, ulnar and cutaneous anterobrachial median nerves was seen, as well as MEP amplitudes recorded from the abductor pollicis brevis muscle. The provocative RHT combined with sEMG and MEP recordings can be considered accurate and objective clinical neurophysiology tools that could supplement the commonly used clinical tests. Such an approach may result in a more precise neurogenic TOS diagnostic algorithm.

Numerical simulation of the fluid-solid coupling mechanism of water and mud inrush in a water-rich fault tunnel

This study developed a new model, a 3D coupled computational fluid dynamics (CFD)-discrete element method (DEM) model, by coupling two software programs, ABAQUS and PFC3D, to solve problems related to fluid-solid interaction systems. The complete governing equations and the two-way coupling process between the two software are presented herein. Via Transmission Control Protocol (TCP) socket communication with Python scripting, information between the two software is exchanged in real-time. Then, the classic example in the PFC5.0 documentation was used to verify the model. In the end, the ABAQUS-PFC3D model was employed to simulate the process of water and mud inrush in a water-rich fault tunnel, which could reflect the evolution process of water and mud inrush and track particle movement in a fault zone. The results show that the particles that collapsed inside the fault formed an ellipsoidal distribution during the water and mud inrush in a water-rich fault tunnel. With the continuous loss of particles in the fault into the tunnel, the migration of particles is discontinuous, and a large void appears inside the fault zone. The rapid change of the groundwater flow velocity caused the negative pore pressure. The pressure arch force structure is formed above the ellipsoidal collapse area inside the fault. The principal force field of the fault areas changes from close to the dip of the fault to close to the perpendicular to the fault.

Numerical investigation on competitive mechanism between internal and external effects of submarine pipeline undergoing vortex-induced vibration

This work aims to model and explore the competitive mechanism between the internal flow effect (IFE) and external current effect (ECE) on the cross-flow vortex-induced vibration (VIV) of a free-span submarine pipeline transporting an axial internal flow. Considering the coupling between the structure and fluids, the partial differential equations of pipeline system are described by Euler-Bernoulli beam theory coupled with the wake oscillator model. To obtain the VIV response of pipeline at different internal flow and external current velocities, the generalized finite difference method (GFDM) and Houbolt method (HM) are employed for spatial and temporal discretizations for equations, respectively. The results indicates that when the IFE is not accounted, the higher-order VIV modes of the pipe are successively excited by ECE. Of interest is that coupling flutter phenomenon between even-order and adjacent modes will occur. Whereas, when the fluid inside the pipe flows, which means the IFE occurrence to be observed, the coupled flutter phenomenon disappears along with significant enlargement of the amplitude in even-order modes. Meanwhile, the mode transition is associated with internal flow velocity and a continuous change in the external flow velocity.

The effect of relative cerebral hyperperfusion during cardiac surgery with cardiopulmonary bypass to delayed neurocognitive recovery.

Delayed neurocognitive recovery (dNCR) remains a common complication after surgery and the incidence of it is determined 30-80% after cardiac surgery with cardiac bypass (CPB) in eldery patients. Many researchers have identified that neuropsychological complications emerge from insufficient cerebral perfusion. Relative cerebral hyperperfusion also disrupts cerebral autoregulation and might play a significant role in dNCR development. The aim of this study is to determine hyperperfusion in the middle cerebral artery during CPB influence to dNCR development and brain biomarker glial fibrillary acidic protein (GFAP) impact in diagnosing dNCR. This prospective - case control study included patients undergoing elective coronary artery bypass grafting or/and valve surgery with CPB. For cognitive evaluation 101 patients completed Addenbrooke's cognitive examination - ACE-III. To determine mild cognitive dysfunction, cut - off 88 was chosen. Mean BFV was monitored with transcranial Doppler ultrasonography (TCD) and performed before surgery, after induction of anaesthesia, during CPB and after surgery. Preoperative BFV was converted to 100% and used as a baseline. The percentage change of cerebral blood flow velocity during CPB was calculated from baseline. Patients with decreased blood flow velocity were included for further investigation. To measure glial fibrillary acidic protein, blood samples were collected after anaesthesia induction, 24 and 48 h after the surgery. According to the ACE-III test results, patients with relative hyperperfusion were divided into two groups: with Delayed neurocognitive recovery and without dNCR (non-dNCR group). 101 patients were examined, 67 (69.1%) men and 29 (29.9%) women, age 67.9 (SD 9.2) Increased percentage of BFV was determined for 40 (39.60%) patients. There were no differences in sex, haematocrit, paCO2, aortic cross-clamping or CPB time between the two groups. Percentage change of BFV was 105.60% in the non-dNCR group and 132.29% in the dNCR group, p = .033. Patients who developed dNCR in the early post-surgical period were significantly older, p < .001 and had a lower baseline of BFV, p = .004. GFAP concentration significantly increased in the dNCR group 48hours after surgery, compared to the non-dNCR group, p = .01. Relative hyperperfusion during CPB may cause dNCR. Elderly patients are sensitive to blood flow velocity acceleration during CPB. GFAP concentration increased 48 h after surgery in dNCR group but did not have any connection with risk factors.

Establishment of rat allogenic vein replacement model and pathological characteristics of the replaced vessels.

BackgroundWith the advancement of vascular anastomosis techniques in recent years, radical surgery for tumors combined with venous vascular resection and reconstruction has been widely used. This study intends to establish two different rat vein replacement models, and further analyze the pathological changes of blood vessels after replacement.MethodsBrown-Norway (BN) rats were selected as donors and recipients, randomly divided into control group, cuff group (1-week group, 2-week group, and 4-week group), and suture group (1-week group, 2-week group, and 4-week group), with 6 rats in each group. The perioperative conditions, inner diameter, flow velocity and histopathological changes of the replaced vessels at different time points were analyzed.ResultsBoth cuff group and suture group can safely establish the rat vein replacement model. From the surgical operation, the operation time and venous cross-clamp time in the cuff group were shorter than those in the suture group (P < 0.05). At 2 and 4 weeks after operation, the diameter of suture group was wider than that of cuff group, and the flow rate was faster (P < 0.05). With prolonged postoperative survival, the wall of the replaced vessels underwent infiltration of CD4+ and CD8+ lymphocytes and high TGF-β1 gene expression. This leads to the proliferation of blood vessels and intimal layer. The results of vascular pathological staining showed that the infiltration degree of CD4+ lymphocytes at 2 weeks after operation and CD8+ lymphocytes at 4 weeks after operation in the suture group was lighter than that in the cuff group (P < 0.05). Meanwhile, TGF-β1 gene content at 4 weeks after operation in suture group was significantly lower than that in cuff group (P < 0.05).ConclusionCompared with cuff method, suture method is more suitable for the study of long-term pathological changes after vein replacement in rats. The main pathological changes in the long term after venous replacement in syngeneic background may be vascular fibrosis caused by inflammatory cell infiltration.

Mechanism comparisons of transport-deposition-reentrainment between microplastics and natural mineral particles in porous media: A theoretical and experimental study

The migration and distribution of microplastic particles (MPs) in the natural environment has attracted global attention in recent years. However, little is known about the transport-deposition-reentrainment differences between MPs and natural mineral particles in porous media. In this study, polystyrene (PS) and silica (SiO2) particles, representing model MPs and natural mineral particles, respectively, were selected to study the responses of different particle types to changes in specific particle size and flow velocity. Three typical particle sizes and various flow velocities were chosen to compare and delineate the transport-deposition-reentrainment characteristics of PS and SiO2 in a packed-bed laboratory column. Collector efficiency was calculated using Tufenkji and Elimelech (TE) equation. The particle fractions released from the collector surfaces were predicted using DLVO theory and force analysis. Two types of particles were attached in the secondary minimum, which were either retained on the collector surface or reentrained to the fluid. The staged elution experiment wherein the flow velocity was increased experienced a period of flow shock, thus breaking the force balance of the particle. An increase in the flow velocity resulted in various degrees of particle elution. The breakthrough experiment at a specific flow velocity showed that the corresponding velocity alteration in staged elution experiment contributed to reentrainment to varying extents. When the effect of gravity on particle deposition was negligible, the particle size was larger, and the lower the velocity for releasing the particles. However, the opposite tendency was observed when considering the effect of gravity on particle deposition. Moreover, the deposition, mainly due to gravity, easily causes particle reentrainment as the flow velocity increases. This study further predicts and reveals the nature of transport and deposition differences between MPs and natural mineral particles, which helps to further assess the risk and potential of groundwater contamination with MPs of different sizes.

Changes in Glaciers and Glacial Lakes in the Bosula Mountain Range, Southeast Tibet, over the past Two Decades

Glaciers and glacial lakes in the Bosula Mountain Range need special attention, because their instability may cause disastrous consequences to the downstream settlements and the Sichuan-Tibet Road. The latter is a pivotal traffic line in the Southeast Tibetan Plateau. In order to investigate the state of glaciers and glacial lakes in the Bosula Mountain Range, we estimated the changes in glacier/glacial lake boundaries, glacier surface elevation, and glacier flow velocity between 2000 and 2021 based on multisource remote sensing data. Our results showed that, from the period 2000–2013 to the period 2013–2021, the average shrinking rate of glacier area increased from 0.99 km2/a to 1.74 km2/a, and the average expanding rate of glacial lake area increased from 0.04 km2/a to 0.06 km2/a. From the period 1990–2011 to the period 2015–2019, the average thinning rate of glaciers increased from 0.83 m/a to 1.58 m/a. These results indicate the Bosula Mountain Range is one of the fastest melting glacierized regions in the High Mountain Asia, and the factors that account for this may include quick temperature rise, abundant summer rainfall, and thin debris cover. In spite of strong ice melting, the observed changes in glacier boundaries, surface elevation, and flow velocity show no sign of surge activity, and the frequency of glacier lake outburst has not increased since 1989. Currently, three proglacial lakes that expanded quickly during 2000–2021 are now prominent hazards. They are directly threatened by accidental ice calving and ice avalanche, and their outburst could cause considerable damage to the downstream settlements and the Sichuan-Tibet Road.

Existence of multiple solutions for magnetohydrodynamic flows of second-grade and Walter’s B fluids due continuously contracting flat sheet with partial slip

In the present investigation, an attempt is performed to analyse the existence of multiple exact solutions for magnetohydrodynamic flows of second-grade and Walter’s B fluids due continuously contracting flat sheet with partial slip condition at the boundary. After transforming basic governing equations by suitable similarity transformations, single and double closed-form exact solutions of the flow are achieved on certain restrictions on flow variables of two aforesaid fluids. The impacts of magnetic field and partial slip on existence and non-existence of solutions are revealed. The changes of flow surface drag and velocity with various involved parametric values are also explored. For both viscoelastic type fluids, i.e., second-grade and Walter’s B fluids, double solutions exist for certain flow conditions. In second-grade case, if viscoelastic parameter exceeds a definite value, then double similarity solutions are achieved for any type of flow, i.e., slip flow or no-slip flow. For Walter’s B fluid similar results are obtained with unique similarity slip flow solution if magnitude of viscoelastic parameter exceeds certain fixed value. Importantly, the magnetic field and its MHD effect stabilize the uncertainty situation in existence of similarity solution for both fluids and produce unique solution for a suitable choice.

Light-driven flow control in the hydrogel microchannel by utilizing a metal microstructure fabricated by multiphoton photoreduction

The light-stimulated control of flow velocity in the hydrogel microchannel was demonstrated by utilizing a metal microstructure fabricated by multiphoton photoreduction. The metal microstructure was fabricated adjacent to the microchannel in a poly-N- isopropylacrylamide (PNIPAm) hydrogel. Owing to the photothermal conversion at the metal microstructure, local deformation of the microchannel and change in flow velocity was induced as a result of the volume phase transition of the supporting hydrogel around the metal microstructure. Wavelength-selective change in the flow velocity was realized by utilizing dissimilar metal microstructures, that exhibit different optical resonances. The results indicate that multiphoton photoreduction is a promising method for fabricating novel hydrogel devices having flow-controllable switches by arranging light-absorbing structures with high spatial selectivity.

A Comparative Study of the Right and Left Carotid Arteries in Relation to Age for Patients With Diabetes and Hypertension

Introduction: Age, hypertension, and diabetes can cause significant alterations in arterial structure and function, including changes in lumen diameter (LD), intimal-medial thickness (IMT), flow velocities, and arterial compliance. These are also considered risk markers of atherosclerosis and cerebrovascular disease. A difference between right and left carotid artery blood flow and IMT has been reported by some researchers, and a difference in the incidence of nonlacunar stroke has been reported between the right and left brain hemispheres. The aim of this study was to determine whether there are differences between the right and left common carotid arteries and internal carotid arteries in patients with hypertension and diabetes for 2 age groups. Methods: We studied 250 patients with both diabetes and hypertension. Patients were divided into 2 age groups with the old age group being 56 to 75 years and the young age group 35 to 55 years. The bilateral common carotid and internal carotid arteries were evaluated with B-mode ultrasound and Doppler examinations. The LD and IMT were measured for both common carotid arteries, and spectral waveform parameters and indices were recorded for both internal carotid arteries. Results: The difference in LD between the left and right common carotid arteries for the old age group was 11.64% and for the young age group was 6.42%, with significant P values of &lt;.05 for both age groups. The difference in IMT between the left and right common carotid arteries was 18.27% in the old age group compared with 15.38% in the young age group, with significant P values of &lt;.05. There was a difference in peak systolic velocity between the left and right internal carotid arteries of 4.85% in the old age group which was not significant, compared with 14.28% in the young age group with a significant P value &lt;.05, whereas the difference in end-diastolic velocity between the left and right internal carotid arteries was not significant for both age groups. Differences between the right and left internal carotid arteries for resistive index, pulsatility index, and pressure gradient were significant only in the young age group. Conclusion: We found significant differences between the right and left common carotid and internal carotid arteries in patients with diabetes and hypertension which were more prominent in the young age group. Values for common carotid IMT and LD were significantly higher in the left common carotid artery versus the right common carotid artery in both age groups. Differences between the 2 carotid sides may be attributed to anatomic variations in the common carotid artery origins which lead to differences in stress between the 2 sides.

Toward a Better Understanding of Muscle Microvascular Perfusion During Exercise in Patients With Peripheral Artery Disease: The Effect of Lower-Limb Revascularization

Purpose: Leg muscle microvascular blood flow (perfusion) is impaired in response to maximal exercise in patients with peripheral artery disease (PAD); however, during submaximal exercise, microvascular perfusion is maintained due to a greater increase in microvascular blood volume compared with that seen in healthy adults. It is unclear whether this submaximal exercise response reflects a microvascular impairment, or whether it is a compensatory response for the limited conduit artery flow in PAD. Therefore, to clarify the role of conduit artery blood flow, we compared whole-limb blood flow and skeletal muscle microvascular perfusion responses with exercise in patients with PAD (n=9; 60±7 years) prior to, and following, lower-limb endovascular revascularization. Materials and Methods: Microvascular perfusion (microvascular volume × flow velocity) of the medial gastrocnemius muscle was measured before and immediately after a 5 minute bout of submaximal intermittent isometric plantar-flexion exercise using contrast-enhanced ultrasound imaging. Exercise contraction-by-contraction whole-leg blood flow and vascular conductance were measured using strain-gauge plethysmography. Results: With revascularization there was a significant increase in whole-leg blood flow and conductance during exercise (p<0.05). Exercise-induced muscle microvascular perfusion response did not change with revascularization (pre-revascularization: 3.19±2.32; post-revascularization: 3.89±1.67 aU.s−1; p=0.38). However, the parameters that determine microvascular perfusion changed, with a reduction in the microvascular volume response to exercise (pre-revascularization: 6.76±3.56; post-revascularization: 2.42±0.69 aU; p<0.01) and an increase in microvascular flow velocity (pre-revascularization: 0.25±0.13; post-revascularization: 0.59±0.25 s−1; p=0.02). Conclusion: These findings suggest that patients with PAD compensate for the conduit artery blood flow impairment with an increase in microvascular blood volume to maintain muscle perfusion during submaximal exercise. Clinical Impact The findings from this study support the notion that the impairment in conduit artery blood flow in patients with PAD leads to compensatory changes in microvascular blood volume and flow velocity to maintain muscle microvascular perfusion during submaximal leg exercise. Moreover, this study demonstrates that these microvascular changes are reversed and become normalized with successful lower-limb endovascular revascularization.