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The flow of an incompressible power-law fluid through a convergent channel is considered, where the viscosity is chosen to be pressure dependent. Instead of utilizing the classical similarity transformation traditionally employed when considering Jeffery-Hamel flow, allowing for purely radial solutions for the velocity field, we allow for flow in both the radial and angular directions. We develop a numerical scheme that conserves the pressure-dependent viscosity at each cell in the computational grid. We recover the classical solution to the problem, and through our numerical solutions, we observe not only that the tangential velocities are not negligible, but also that flow reversal occurs, as illustrated by solutions with varying flow regimes. Decreasing the angle of the channel causes the magnitude of the velocity to decrease, while shorter channels lead to an increase in the magnitude of the radial and tangential velocities. In the case of the latter, this could indicate that in shorter channels, the tangential velocity has a larger impact on the occurrence of flow reversal. For more varied flow regimes, the magnitude of the radial and tangential velocities increases. [ABSTRACT FROM AUTHOR]

Preoperative anemia is associated with worse postoperative morbidity and mortality after major vascular procedures. Limited research has examined the optimal method of carotid revascularization in patients with anemia. Therefore, we aim to compare the postoperative outcomes after carotid endarterectomy (CEA), transfemoral carotid artery stenting (TFCAS), and transcarotid artery revascularization (TCAR) among patients with anemia. This is a retrospective review of patients with anemia undergoing CEA, TFCAS, and TCAR in the Vascular Quality Initiative database between 2016 and 2023. We defined anemia as a preoperative hemoglobin level of <13 g/dL in men and <12 g/dL in women. The primary outcomes were 30-day mortality and in-hospital major adverse cardiac events (MACE). Logistic regression models were used for multivariate analyses. Our study included 40,383 CEA (59.3%), 9159 TFCAS (13.5%), and 18,555 TCAR (27.3%) cases in patients with anemia. TCAR patients were older and had more medical comorbidities than CEA and TFCAS patients. TCAR was associated with a decreased 30-day mortality (adjusted odds ratio [aOR], 0.45; 95% confidence interval [CI], 0.37-0.59; P <.001), in-hospital MACE (aOR, 0.58; 95% CI, 0.46-0.75; P <.001) compared with TFCAS. Additionally, TCAR was associated with a 20% decrease in the risk of 30-day mortality (aOR, 0.80; 95% CI, 0.65-0.98; P =.03) and a similar risk of in-hospital MACE (aOR, 0.86; 95% CI, 0.77-1.01; P =.07) compared with CEA. Furthermore, TFCAS was associated with an increased risk of 30-day mortality (aOR, 2; 95% CI, 1.5-2.68; P <.001) and in-hospital MACE (aOR, 1.7; 95% CI, 1.4-2; P <.001) compared with CEA. In this multi-institutional national retrospective analysis of a prospectively collected database, TFCAS was associated with a high risk of 30-day mortality and in-hospital MACE compared with CEA and TCAR in patients with anemia. TCAR was associated with a lower risk of 30-day mortality compared with CEA. These findings suggest TCAR as the optimal minimally invasive procedure for carotid revascularization in patients with anemia. [ABSTRACT FROM AUTHOR]

The Centers for Medicare and Medicaid Services now approve reimbursement for transfemoral carotid artery stenting (TFCAS) in the treatment of standard-risk patients with carotid artery occlusive disease. TFCAS in patients with complex aortic arch anatomy is known to be challenging with worse outcomes. Transcarotid artery revascularization (TCAR) could be a preferable alternative in these patients owing to avoiding the aortic arch and using flow reversal during stent deployment. We aim to compare the outcomes of TCAR vs TFCAS across all aortic arch types and degrees of arch atherosclerosis. All patients undergoing carotid artery stenting between September 2016 and October 2023 were identified in the Vascular Quality Initiative database. Patients were stratified into four groups: Group A (mild atherosclerosis and type I/II arch), Group B (mild atherosclerosis and type III arch), Group C (moderate/severe atherosclerosis and type I/II arch), and Group D (moderate/severe atherosclerosis and type III arch). The primary outcome was in-hospital composite stroke or death. Analysis of variance and χ2 tests analyzed differences for baseline characteristics. Logistic regression models were adjusted for potential confounders, and backward stepwise selection was implemented to identify significant variables for inclusion in the final models. Kaplan-Meier survival estimates, log rank test, and multivariable Cox regression models analyzed hazard ratios for 1-year mortality. A total of 20,114 patients were included (Group A: 12,980 [64.53%]; Group B: 1175 [5.84%]; Group C: 5124 [25.47%]; and Group D: 835 [4.15%]). TCAR was more commonly performed across the four groups (72.21%, 67.06%, 74.94%, and 69.22%; P <.001). Compared with patients with mild arch atherosclerosis, patients with advanced arch atherosclerosis in Group C and Group D were more likely to be female, hypertensive, smokers, and have chronic kidney disease. Patients with type III arch in Group B and Group D were more likely to present with stroke preoperatively. On multivariable analysis, TCAR had less than one-half the risk of stroke/death and 1-year mortality compared with TFCAS in the patients with the mildest atherosclerosis and simple arch anatomy (Group A) (odds ratio [OR], 0.43; 95% confidence interval [CI], 0.31-0.61; P <.001; hazard ratio, 0.42; 95% CI, 0.32-0.57; P <.001). Group B patients with similar atherosclerosis but more complex arch anatomy had 70% lower odds of stroke/death with TCAR compared with TFCAS (OR, 0.30; 95% CI, 0.12-0.75; P =.01). Similar findings were also evident in patients with more severe atherosclerosis and simple arch anatomy (OR, 0.66; 95% CI, 0.44-0.97; P =.037). There was no significant difference in odds of stroke/death in patients with advanced arch atherosclerosis and complex arch (Group D) (OR, 0.91; 95% CI, 0.39-2.16; P =.834). TCAR is safer than TFCAS in patients with simple and advanced arch anatomy. This could be related to the efficiency of flow reversal vs distal embolic protection. The current Centers for Medicare and Medicaid Services decision will likely increase stroke and death outcomes of carotid stenting nationally if multidisciplinary approach and appropriate patient selection are not implemented. [ABSTRACT FROM AUTHOR]

Carotid artery restenosis after index carotid artery revascularization reduces its stroke prevention benefit. A 73-year-old woman presented with recurrent right carotid artery restenosis following two carotid endarterectomies with patch angioplasty and in-sent restenosis after subsequent transcarotid artery revascularization. We performed in-stent paclitaxel-coated balloon angioplasty under flow reversal with resolution of the lesion on imaging and improvement in symptoms. Patient remains asymptomatic with no evidence of restenosis 16 months after treatment.

This investigation focuses on the flow reversal and separation of hybrid nanofluid, with heat generation and first-order velocity slip, in a Darcy porous medium. The Choi–Eastman nanofluid model is used to formulate the hybrid nanofluid mathematical model. Suitable similarity transformations convert partial differential equations into a system of ordinary differential equations. The resultant systems are numerically solved by implementing the shooting approach. Multiple solutions are found for this current problem, and intriguingly, the velocity and temperature profiles of these two solution branches exhibit opposing characteristics. In conclusion, conducting a stability study on these two alternative solutions is worthwhile to determine which solution is more realistic and stable. The temporal stability test reveals that only the first solution is stable or physically valid. The important outcomes of this study, based on the stable solutions, are as follows: (i) the hybrid nanofluid's Nusselt number, skin friction, and velocity rise when the inclined magnetic parameter rises, (ii) the value of the smallest eigenvalue increases with higher values of the inclined magnetic parameter, and (iii) the thickness of momentum and thermal boundary layers is thinner for the first solution than the second solution. Additionally, the identification of flow separation and reversal points is valuable for aerospace technology, following the Prandtl theory. Finally, this study provides streamlined patterns to enhance the understanding of fluid flow behavior. [ABSTRACT FROM AUTHOR]

The flow of an incompressible power-law fluid through a convergent channel is considered, where the viscosity is chosen to be pressure dependent. Instead of utilizing the classical similarity transformation traditionally employed when considering Jeffery-Hamel flow, allowing for purely radial solutions for the velocity field, we allow for flow in both the radial and angular directions. We develop a numerical scheme that conserves the pressure-dependent viscosity at each cell in the computational grid. We recover the classical solution to the problem, and through our numerical solutions, we observe not only that the tangential velocities are not negligible, but also that flow reversal occurs, as illustrated by solutions with varying flow regimes. Decreasing the angle of the channel causes the magnitude of the velocity to decrease, while shorter channels lead to an increase in the magnitude of the radial and tangential velocities. In the case of the latter, this could indicate that in shorter channels, the tangential velocity has a larger impact on the occurrence of flow reversal. For more varied flow regimes, the magnitude of the radial and tangential velocities increases.

Objective: Transcarotid artery revascularization (TCAR) has emerged as a safe and effective method for carotid revascularization, offering several key advantages over carotid endarterectomy (CEA) and carotid artery stenting (CAS). Intraoperative transcranial Doppler (TCD) monitoring plays a pivotal role in assessing cerebral hemodynamics and detecting embolic signals during TCAR at our institution. Methods: This review synthesizes the current literature and provides guidance for TCD monitoring throughout the various phases of TCAR, from preoperative assessment to postoperative management. Key considerations include probe placement, waveform evaluation, interpreting monitoring parameters such as mean flow velocity (MFV), pulsatility index (PI), and percentage change in the MFV (Δ%). Techniques for maintaining the insonation of the middle cerebral artery (MCA) M1 segment and optimal parameter settings for intraoperative TCD monitoring are detailed. Results: TCAR phases are highlighted, including transcarotid access and vessel control, sheath insertion, the establishment of flow reversal, pre-dilation, stent placement, post-dilation, and closure, while emphasizing the importance of real-time feedback provided by TCD monitoring in identifying embolic signals and assessing changes in cerebral perfusion. The review discusses limitations of TCD monitoring, such as inadequate temporal windows, incorrect vessel identification and reliability issues with automatic emboli detection counters. Furthermore, practical advice is provided on how to navigate common pitfalls encountered during intraoperative TCD monitoring. Conclusion: By understanding the nuances of TCD monitoring and its application in TCAR, intraoperative TCD monitoring may aid to minimize the low but potential risk of intraprocedural embolic events, periprocedural hypoperfusion and postoperative hyperperfusion. Finally, we suggest opportunities for further research in embolization quantification and additional strategies to optimize quality control in TCAR.

A case of a 74 year old female with a prior history of right carotid endarterectomy (CEA) followed by carotid interposition bypass with polytetrafluoroethylene (PTFE) graft several years later due to restenosis. At 1 year follow up, she was found to have low velocities in the bypass and reversal of flow in her right vertebral artery indicating proximal stenosis. A computed tomography angiography (CTA) and magnetic resonance angiography (MRA) were obtained showing high grade occlusive lesion at her innominate artery. After an unsuccessful attempt at transfemoral endovascular intervention, the patient was brought back for a transcarotid retrograde approach utilizing ENROUTE ® Neuroprotection System with flow reversal for embolic protection. The lesions was crossed successfully in this approach and a balloon mounted covered stent was deployed using Gore ® VBX stent. There was significant amount of debris in the filter which would have embolized without neuroprotection. Patient was discharged on postoperative day 1 with no neurological deficits. In conclusion, this case highlights a successful use of ENROUTE ® Neuroprotection System flow reversal for retrograde transcarotid approach to treat difficult innominate lesions with satisfactory embolic protection.

Transcarotid artery revascularization (TCAR) has emerged as an alternative to carotid artery stenting (CAS). TCAR demonstrated its superiority by avoiding femoral artery puncture and establishing proximal protection without crossing the stenotic lesion. In the TCAR era, we focused on the possibility of a trans-distal radial approach (DRA). A balloon-guide catheter was navigated via DRA to establish proximal protection before lesion crossing. The forearm subcutaneous vein was used as the flow-reversal circuit. Six internal carotid artery stenosis patients underwent CAS using "the forearm flow reversal technique." Every procedure was performed under continuous flow reversal from the common carotid artery to the forearm cephalic vein. Successful revascularization was achieved without ischemic or access-site complications. The distal radial artery was patent at discharge in all cases. Trans-distal radial CAS with forearm flow reversal is a feasible and less invasive technical option. [ABSTRACT FROM AUTHOR]

Neuroendovascular treatment via transradial access (TRA) has gained popularity as a minimally invasive technique. However, the flow reversal (FR) system, reported useful in carotid artery stenting (CAS), cannot be applied via TRA because it requires an access route of more than 8 F. Herein, we report the utility of a modified FR system applied via TRA using a sheathless 8-F balloon guide catheter and a 2.6-F balloon catheter. In a retrospective analysis of a single-center consecutive case series, patients with CAS and vulnerable plaques who were treated with CAS via TRA using a modified FR system from June 2022 to August 2022 were examined. High-intensity spots were assessed on postprocedural diffusion-weighted magnetic resonance images. Puncture site complications at discharge and cardiovascular events for 1 year after CAS were also evaluated. Ten patients were included in this study. There were no high-intensity spots on diffusion-weighted magnetic resonance images after CAS. No procedure-related complications, including radial artery occlusion or cardiovascular events, were observed. This study suggests that CAS with FR using our modified system is feasible via TRA and may be an effective technique with a low rate of vascular complications. [ABSTRACT FROM AUTHOR]

BackgroundPoststent ballooning/angioplasty (post-SB) have been shown to increase the risk of stroke risk after transfemoral carotid artery stenting. With the advancement of transcarotid artery revascularization (TCAR) with dynamic cerebral blood flow reversal, we aimed to study the impact of post-SB during TCAR.MethodsPatients undergoing TCAR in the Vascular Quality Initiative between September 2016 and May 2019 were included and were divided into three groups: those who received prestent deployment angioplasty only (pre-SB, reference group), those who received poststent deployment ballooning only (post-SB), and those who received both prestent and poststent deployment ballooning (prepost-SB). Patients who did not receive any angioplasty during their procedure (n = 367 [6.7%]) were excluded because these represent a different group of patients with less complex lesions than those requiring angioplasty. Primary outcome was in-hospital stroke or death. Analysis was performed using univariable and multivariable logistic regression models.ResultsOf 5161 patients undergoing TCAR, 34.7% had pre-SB only, 25% had post-SB only, and 40.3% had both (prepost-SB). No differences in the rates of in-hospital and 30-day stroke, death, and stroke/death were observed among the three groups; in-hospital stroke/death in the pre-SB group was 1.4% (n = 25), post-SB 1.2% (n = 16), and prepost-SB 1.4% (n = 29; P = .92). However, patients undergoing post-SB and prepost-SB had higher rates of in-hospital transient ischemic attacks (TIA) (post-SB, 0.9%; prepost-SB, 1% vs pre-SB, 0.2%, P < .01) and postprocedural hypotension (16.6% and 16.8% vs 13.1%, respectively; P < .001). Post-SB also had longer operative times, as well as flow reversal and fluoroscopy times. On multivariable analysis, no association was seen between post-SB and the primary outcome of in-hospital stroke/death (post-SB odds ratio [OR], 0.88; 95% confidence interval [CI], 0.44-1.73; prepost-SB OR, 0.98; 95% CI, 0.57-1.70). Similarly, no significant differences were noted in terms of postprocedural hemodynamic instability and 30-day outcomes. However, post-SB and prepost-SB were associated with four times the odds of in-hospital TIA compared with pre-SB alone (post-SB OR, 4.24 [95% CI, 1.51-11.8]; prepost-SB OR, 4.76 [95% CI, 1.53-14.79]; P = .01). Symptomatic patients had higher rates of in-hospital stroke/death compared with their asymptomatic counterparts; however, there was no significant interaction between symptomatic status and ballooning in predicting the primary outcome.ConclusionsPost-SB was used in 65.3% of TCAR patients. This maneuver seems to be safe without an increase in the odds of postoperative in-hospital stroke/death. However, the increased rates of TIA associated with post-SB requires further investigation.

ObjectiveThe current recommendations are to perform carotid endarterectomy within 2 weeks of symptoms for maximum long-term stroke prevention, although urgent carotid endarterectomy within 48 hours has been associated with increased perioperative stroke. With the development and rapid adoption of transcarotid artery revascularization (TCAR), we decided to study the effect of timing on the outcomes after TCAR.MethodsThe Vascular Quality Initiative database was searched for symptomatic patients who had undergone TCAR from September 2016 to November 2019. These patients were stratified by the interval to TCAR after symptom onset: urgent, within 48 hours; early, 3 to 14 days; and late, >14 days. The primary outcome was the in-hospital rate of combined stroke and death (stroke/death), evaluated using logistic regression analysis. The secondary outcome was the 1-year rate of recurrent ipsilateral stroke and mortality, evaluated using Kaplan-Meier survival analysis.ResultsA total of 2608 symptomatic patients who had undergone TCAR were included. The timing was urgent for 144 patients (5.52%), early for 928 patients (35.58%), and late for 1536 patients (58.90%). Patients undergoing urgent intervention had an increased risk of in-hospital stroke/death, which was driven primarily by an increased risk of stroke. No differences were seen for in-hospital death. On adjusted analysis, urgent intervention resulted in a threefold increased risk of stroke (odds ratio [OR], 2.8; 95% confidence interval [CI], 1.3-6.2; P = .01) and a threefold increased risk of stroke/death (OR, 2.9; 95% CI, 1.3-6.4; P = .01) compared with late intervention. Patients undergoing early intervention had comparable risks of stroke (OR, 1.3; 95% CI, 0.7-2.3; P = .40) and stroke/death (OR, 1.2; 95% CI, 0.7-2.1; P = .48) compared with late intervention. On subset analysis, the type of presenting symptoms was an effect modifier. Patients presenting with stroke and those presenting with transient ischemic attack or amaurosis fugax both had an increased risk of stroke/death when undergoing urgent compared with late TCAR (OR, 2.7; 95% CI, 1.1-6.6; P = .04; and OR, 4.1; 95% CI, 1.1-15.0; P = .03, respectively). However only patients presenting with transient ischemic attack or amaurosis fugax had experienced an increased risk of stroke with urgent compared with late TCAR (OR, 5.0; 95% CI, 1.4-17.5; P < .01). At 1 year of follow-up, no differences were seen in the incidence of recurrent ipsilateral stroke (urgent, 0.7%; early, 0.2%; late, 0.1%; P = .13) or postdischarge mortality (urgent, 0.7%; early, 1.6%; late, 1.8%; P = .71).ConclusionsWe found that TCAR had a reduced incidence of stroke when performed 48 hours after symptom onset. Urgent TCAR within 48 hours of the onset of stroke was associated with a threefold increased risk of in-hospital stroke/death, with no added benefit for ≤1 year after intervention. Further studies are needed on long-term outcomes of TCAR stratified by the timing of the procedure.

Turbidity source apportionment is essential but complex for precise environmental rehabilitation of worldwide urban lakeside river networks impaired by turbidity. A new turbidity source analysis framework including in-situ sampling, vessel monitoring, remote sensing, and hydrodynamic modelling was proposed, where the critical processes of flow reversal from the turbid lake, navigation, and urban non-point source in urban lakeside river networks were explicitly considered. The case study results showed that the turbidity problem (mean value was 211.3 nephelometric turbidity units (NTU)) was primarily led by suspended inorganic matter (58%), followed by suspended organic matter (19%) and other matter. The Tiaoxi River and busy shipping contributed most to the annual total suspended solids load of the target river, with the same percentage of 34%. The turbid Lake Taihu provided 64,663 tonnes and 31% of the total suspended solids load, focusing on the autumn and winter months. Tiaoxi River load was highly concentrated on the storm events, which accounted for 71.4% of the annual Tiaoxi River source (209846 tonnes). The large water volume of reverse flow and the high TSS concentration of Lake Taihu in the autumn and winter months accounted for the seasonal change in Lake Taihu’s TSS load. The coronavirus disease lockdown reduced the mean monthly total suspended solids concentration of 152.4 mg/L in November and December 2019 to 49.2 mg/L in January and February 2020, by limiting the waterway transportation and the market demand for building materials. The river estuary’s vegetation interception belt, shipping restriction and rerouting, and integrated catchment management were advised to mitigate the urban river network turbidity.

To optimize the flow field in a tubular reactor, new flow deflectors were added by using flow reversal technology. Two optimization structures, namely asterisk plate and composite plate, were designed. Numerical simulation was combined with physical experiments to verify the effectiveness of the flow field optimization. The results showed that the flow field uniformity of the reactor could be greatly improved by single plate and double plate. The uniformity index of the velocity in the axial section is greater than 0.95 within 15 cm, and the physical simulation results conform to the overall trend of the numerical simulation. However, the length of the optimized area of the single plate is about 5 cm shorter than that of the double plate, and it has better stability in the physical model. [ABSTRACT FROM AUTHOR]

Ducts are conduits or passages used to supply, return, or exhaust air, needed for heating, ventilation, or air conditioning in multistory gigantic building structures. Rapid growth in population (especially in industrially concentrated regions) has led to the culture of constructing skyscrapers of tens of storeys, in which vertical ducts are the natural choice for removing polluted air. Due to the compactness of the building design, high voltage current-carrying wires are usually located very close to exhaust ducts carrying polluted air. Consequently, a natural motivation is to study how the magnetic field produced by such a wire affects the flow, driven by an external pressure gradient (for example, exhaust fan, vacuum pump, etc.) in a vertical duct. Therefore, the paper is devoted to understanding the interaction of the developed (thermally and hydrodynamically) flow in a vertical square duct with the magnetic field produced by a nearby placed current-carrying wire. The flow is assumed to be laminar and is driven by a constant external pressure gradient. For the thermal boundary condition, we assume a uniform heat flux across the unit axial length whereas a fixed temperature is also assumed over the peripheral surface of the duct. As a result of the mathematical modeling of the problem, we come across a system of coupled Poisson-like equations which are solved numerically by following a finite volume approach. We have noted that a sufficiently higher Rayleigh number may cause a reverse flow while reducing and flattening the thermal distribution in the middle of the duct. In addition the magnetic field further reduces the flow velocity, particularly near the duct wall where the current-carrying wire (causing the magnetic field) is positioned.

This paper describes a detailed catalyst configuration study for a catalytic flow reversal reactor for lean methane combustion using computational modelling. The design is based on the use of a platinum group metals catalyst in the form of a washcoated monolith. A small-scale pilot plant reactor is used as the basis for the study. The computational model is based on the fundamental conservation equations of mass and energy that are solved using the finite element method with commercial software. Extensive model validation is performed using experimental data previously obtained on the pilot plant system. It is found that catalyst activity and length of the reaction section play key roles in the stable operation and performance of the system. For methane feed concentrations above about 0.5% by volume, the catalyst activity plays a relatively small role. For concentrations down to about 0.2% both the catalyst activity and reactor length become increasingly important. The complete transient history of the reactor also plays an important role in determining whether or not a stable stationary state can be achieved for a given set of inlet conditions. Computational modelling is shown to be an extremely valuable tool for the design of the reactor system. [Display omitted] • Catalyst configuration in reverse flow reactor for methane combustion is studied. • Stable operation is achieved at low catalyst activity with higher concentration. • Stable operation at low concentration requires higher catalyst activity. • The length of the catalyst section affects the performance significantly. • System history determines stable operating points. [ABSTRACT FROM AUTHOR]

Objectives: Carotid artery stenting (CAS) is commonly performed through transfemoral or transcarotid access. Neurological protection methods utilized during the procedure include distal embolic protection (DEP) and flow reversal devices. Multiple studies demonstrated more favorable outcomes associated with transcarotid artery revascularization with flow reversal (TCAR) in comparison to transfemoral carotid artery stenting with DEP (TFCAS-DEP). However, not many studies compared TCAR to transcarotid artery stenting with DEP (TCAS-DEP) or TFCAS with flow arrest by proximal balloon occlusion (TFCAS-PBO). We aimed to compare the effect of access types and embolic protection methods on the outcomes of CAS., Methods: All patients undergoing CAS between September 2016 and August 2024 were identified in Vascular Quality Initiative database. Inverse probability of treatment weighting based on propensity scores was used to compare outcomes of TFCAS-DEP, TFCAS-PBO, and TCAS-DEP to TCAR. Cohorts were weighted with regards to 27 baseline variables., Results: A total of 99,030 patients were included in our study: TCAR 66,655 (67.3%); TFCAS-DEP 30,723 (31.0%); TCAS-DEP 912 (0.9%); and TFCAS-PBO 740 (0.8%). Compared to TCAR, TFCAS-DEP had more than double the odds of in-hospital and 30-day mortality [OR=2.68(95%CI 2.25-3.19),p<0.001; OR=2.39(95%CI 2.08-2.74),p<0.001], and 62% higher odds of stroke/death [OR=1.62(95%CI 1.45-1.81),p<0.001]. TCAS-DEP group had double the risk of 30-day mortality [OR=2.00(95%CI 1.13-3.53),p=0.016] and 58% increased risk of stroke [OR=1.58(95%CI 1.04-2.38),p=0.031]. Finally, higher odds of in-hospital and 30-day mortality [OR=2.47(95%CI 1.22-5.00),p=0.012; OR=1.85(95%CI 1.03-3.30),p=0.038] were observed in the TFCAS-PBO group when compared to TCAR., Conclusions: In this large, comprehensive multi-institutional study comparing carotid access types and embolic protection methods, TCAR seems to be the safest endovascular carotid revascularization procedure owing to its lower risk of postoperative stroke or death. This study confirms that avoidance of the aortic arch and flow reversal neuroprotection are both important in reducing complications following CAS., (Copyright © 2025. Published by Elsevier Inc.)

Objective: Transcarotid artery revascularization (TCAR) has been used with increasing prevalence for treatment of carotid artery stenosis. TCAR holds potential benefits over traditional carotid endarterectomy (CEA) or transfemoral carotid artery stenting by its nature of being less invasive than CEA but more neuroprotective than transfemoral carotid artery stenting. The purpose of this pilot study is to evaluate the effectiveness of the neuroprotection system of TCAR with flow reversal by quantifying the incidence and degree of new intracerebral lesions using diffusion-weighted magnetic resonance imaging (DW-MRI). This study is the first to evaluate these findings in a real-world, high-risk cohort, who would have been excluded from the ROADSTER and ENROUTE transcarotid neuroprotection system DW-MRI studies. Methods: Patients undergoing unilateral TCAR for symptomatic or asymptomatic severe internal carotid artery disease were eligible and prospectively enrolled in the study. All patients had high risk features, including comorbidities or medications, which excluded them from industry-sponsored DW-MRI trials. Patients underwent a preoperative DW-MRI to obtain a baseline intracerebral evaluation within 1 week of the scheduled surgery. The follow-up DW-MRI occurred within 48 hours postoperatively. The primary outcome was new, acute postoperative lesion(s) identified on DW-MRI. Secondary outcomes include any major stroke, myocardial infarction, or death during hospitalization. Results: Five consecutive patients underwent TCAR with preoperative and postoperative imaging. All five patients were on dual antiplatelet therapy before their procedure and verified to be therapeutic on these agents. All patients underwent a right-sided TCAR and three were symptomatic as the indication for their procedure. All five patients demonstrated chronic lesions on the preoperative DW-MRI. Technical success was achieved in all five patients, with one operative complication involving a dissection of the common carotid at the access site, which was stented using the TCAR system. Postoperative DW-MRI did not identify any new intracerebral lesions in any patient following the procedure. No patient had a stroke, myocardial infarction, or death during hospitalization. Conclusions: In this real-world, high-risk cohort, TCAR was completed with no evidence of new, postoperative DW-MRI lesions. These data further demonstrate that TCAR with flow reversal is an effective neuroprotective strategy for carotid revascularization. Further study is warranted to evaluate DW-MRI differences between TCAR and CEA.

Ducts are conduits or passages used to supply, return, or exhaust air, needed for heating, ventilation, or air conditioning in multistory gigantic building structures. Rapid growth in population (especially in industrially concentrated regions) has led to the culture of constructing skyscrapers of tens of storeys, in which vertical ducts are the natural choice for removing polluted air. Due to the compactness of the building design, high voltage current-carrying wires are usually located very close to exhaust ducts carrying polluted air. Consequently, a natural motivation is to study how the magnetic field produced by such a wire affects the flow, driven by an external pressure gradient (for example, exhaust fan, vacuum pump, etc.) in a vertical duct. Therefore, the paper is devoted to understanding the interaction of the developed (thermally and hydrodynamically) flow in a vertical square duct with the magnetic field produced by a nearby placed current-carrying wire. The flow is assumed to be laminar and is driven by a constant external pressure gradient. For the thermal boundary condition, we assume a uniform heat flux across the unit axial length whereas a fixed temperature is also assumed over the peripheral surface of the duct. As a result of the mathematical modeling of the problem, we come across a system of coupled Poisson-like equations which are solved numerically by following a finite volume approach. We have noted that a sufficiently higher Rayleigh number may cause a reverse flow while reducing and flattening the thermal distribution in the middle of the duct. In addition the magnetic field further reduces the flow velocity, particularly near the duct wall where the current-carrying wire (causing the magnetic field) is positioned. [ABSTRACT FROM AUTHOR]

Saltwater intrusion is a common feature in the Changjiang Estuary affected by river discharges and tidal flows. It leads to a two‐layer flow structure during the flood‐to‐ebb tidal transient period: the seaward tidal flow in the upper water column and onshore intruded salt flow in the lower column, even though the lower column water usually experiences an ebb flow eventually. Our recent measurements with a tripod deployed in a tidal channel of the North Branch in the East China Sea challenged this feature. We detected that the two‐layer flow structure disappeared in the ebb tide period during the neap cycle due to intense saltwater intrusion. A constant onshore flood‐like flow predominated the entire water column. The physical mechanism for the flow reversal was examined using the Finite Volume Community Ocean Model (FVCOM). The FVCOM was robust to capture the observed flow reversal in the tidal channel during the neap tidal cycle. The momentum balance analysis results suggest that the flow reversal occurred when the saltwater intrusion‐induced onshore baroclinic pressure gradient force and baroclinic tidal rectification overwhelmed the seaward barotropic pressure gradient force. A parameter‐driven criterion was derived theoretically to determine the potential occurrence of a stable ebb flow reversal in the tidal channel. Plain Language Summary: Many estuaries experience saltwater intrusion, bringing saltwater from offshore regions to nearshore and river channels. In the Changjiang Estuary, it could create a two‐layer flow structure during the flood‐to‐ebb transient period, a seaward fresher ebb tidal flow in the upper water column, and an onshore intruded salt flow in the lower water column. Could the increased saltwater intrusion destroy this two‐layer flow structure and form an onshore flow throughout the water column in the ebb‐tidal period during a neap tidal cycle? If it does, what is the critical driving mechanism? To answer these questions, we deployed a tripod system integrated with state‐of‐the‐art marine instruments in a tidal channel of North Branch in the Changjiang Estuary, an area where saltwater intrusion frequently occurs. The observational data captured a flow‐overtured feature, showing a stable flood‐like intruded flow throughout the entire water column in the ebb‐tidal period during a neap tidal cycle. We applied the Finite‐Volume Community Ocean Model to examine the physical driving mechanism for flow‐overturning. The results suggest that the flow‐overturning could occur when the along‐channel saltwater intrusion‐induced baroclinic pressure gradient force and stratified tidal rectification overwhelmed the along‐channel tide‐induced barotropic pressure gradient force. Key Points: The bottom tripod system identified an overturned tidal flow in the North Branch channelA numerical model revealed the baroclinic gradient force from saltwater intrusion dominated the overturnThe balance criteria were proposed to estimate competition between these two dynamics [ABSTRACT FROM AUTHOR]

Appearance of steep property gradients with change in temperature is a fascinating feature of any supercritical fluid, which can instigate intricate dynamics in supercritical natural circulation loops by modulating the effective forces. While most of the relevant literature focuses on stability evaluation, anticipation regarding the transient response of the system during power transition is of utmost significance, especially in high-power applications. Present study aims at furnishing insight on the same by developing a one-dimensional numerical model of a rectangular loop with supercritical CO 2 as the working medium, and characterizing the temporal trends over a wide range of heating power. Two different profiles of power upsurge have been tested for different regimes of heat transfer, unearthing intriguing characteristics. The combination of initial and final regimes during any transformation is found to be the most crucial factor. Single-step rise in power, in general, is the most vulnerable one, specifically during large-scale change of the order of 1000 W, and better be employed only at low-power regime. Even single-step change ∼ 25 W can inflict instability and flow transition within the transition regime. Power transformation following linear ramp profile with transition periods of 5, 10 and 20 s is identified to be the most suitable one across all the regimes. It can successfully mitigate instability even in the later parts of the transition regime, albeit at the expense of greater time requirement to attain the final stable state and possibly a greater period of transformation. Change through multiple small steps (about 250 W for large change in low power regime and 15 W within transition regime) can also be a feasible option for avoiding the growth of unstable oscillations at higher powers. • Numerical investigation of dynamics in supercritical NCL during power upsurge. • Dominating role of initial and final regimes of heat transfer in deciding profile. • Single-step change from 250 W to 1250 W can instigate instability and flow reversal. • Ramp profile with transition span of 5–20 s most suitable even in transition regime. • Change can be facilitated through multiple small steps of 250 W in low-power regime. [ABSTRACT FROM AUTHOR]

• Research reactors with a downward nominal flow direction can experience flow reversal. • The reactor fuel may be damaged if dryout occurs. • Physics of flow reversal in narrow rectangular channels is discussed. • Modelling choices and code correlations are benchmarked providing useful insights. • CATHARE and RELAP5 calculations demonstrate good agreement with experimental data. Flow reversal in narrow coolant channels can be a crucial phenomenon for the safety of research reactors with a downward nominal flow direction. During a loss of forced flow accident, the downward flow stagnates briefly before transitioning into an upward natural circulation flow. The fuel may be damaged if dryout occurs and threshold fuel and/or cladding temperatures are exceeded. A comprehensive study is provided for flow reversal in narrow rectangular channels by examining experimental data and conducting software model analyses. The literature on flow reversal was reviewed, and selected experimental datasets were used to benchmark against CATHARE and RELAP5 models and also compare the code calculations with each other. The experimental data comes from flow reversal tests conducted with a narrow rectangular channel with one-sided heating. The results were compared with experimental data for successful flow reversal tests and predicted dryout power for dryout conditions. Also, the study examined the effects of the pump coastdown period, inlet liquid temperature, system pressure, and localized pressure drops. The experimental results showed that shorter coastdown periods, reduced pressure drops, and lower coolant inlet temperatures increased the dryout power. However, the system pressure did not noticeably affect the results. The simulation results showed that both CATHARE and RELAP5 agreed with experimental data, capturing the trends of the experimental results. Slight differences between each code calculation, as well as the predicted and measured dryout powers, were attributed to experimental uncertainties and the modeling of physical phenomena such as wall nucleation, interfacial heat transfer, drag coefficients, and critical heat flux. Overall, this study provides an understanding of flow reversal and the prediction capabilities of thermal-hydraulics software models. A future study of the flow reversal benchmark of a narrow rectangular channel with two-sided heating may provide additional valuable insights. [ABSTRACT FROM AUTHOR]

• Tonle Sap Lake is a large shallow tropical lake characterized by annual flood pulse. • Phosphorus distribution and bioavailability dynamics were investigated this lake. • The composition, fractions, and bioavailability of P were determined by flood pulse. • Low-water period had higher concentration of bioavailable P than high-water period. This study aims to investigate how the hydrological phase in a flood pulse dominated system, Tonle Sap Lake (TSL), affects the chemical form and bioavailability of P. For this purpose, we conducted extensive field campaigns under different hydrological phases: low-water (LW), rising-water (RW), high-water (HW), and falling-water (FW) phases from December 2016 to September 2017. The TSL ecosystem distinctly exhibited seasonality of the monotonal flood pulse between the low-water and high-water periods, in terms of not only water depth (range 0.5–8.0 m) but also water quality, suspended sediment, P dynamics (concentration, speciation and bioavailability), and trophic status. On an annual basis, the lake retained 56.2% of the external P loads, representing a major sink of P. Seasonally, P dynamics in TSL are determined by internal loading, whereas the annual inflows from the Mekong River basin and lake's tributaries are important sources of P for TSL. Total particulate phosphorus (TPP) constituted >60% of the total P in LW and decreased to <30% during HW, corresponding to the variation in total suspended solids (TSS). Soluble reactive P predominated the total dissolved P during LW (>70%) and decreased to approx. 30% during HW with decreasing TSS and TPP, suggesting the reduction of bioavailability of P in HW. Our results indicate that the flood pulse plays an important role in the chemical form and bioavailability of P in shallow lakes. [ABSTRACT FROM AUTHOR]

Objective: To compare the outcomes of TCAR with flow reversal to the gold standard CEA using data from the Society for Vascular Surgery Vascular Quality Initiative TCAR Surveillance Project. Summary of Background Data: TCAR is a novel minimally invasive procedure for carotid revascularization in high-risk patients that is associated with significantly lower stroke rates compared with carotid artery stenting via the transfemoral approach. Methods: Patients in the United States and Canada who underwent TCAR and CEA for carotid artery stenosis (2016-2019) were included. Propensity scores were calculated based on baseline clinical variables and used to match patients in the 2 treatment groups (n = 6384 each). The primary endpoint was the combined outcome of perioperative stroke and/or death. Results: No significant differences were observed between TCAR and CEA in terms of in-hospital stroke/death [TCAR, 1.6% vs CEA, 1.6%, RR (95% CI): 1.01 (0.77–1.33), P = 0.945], stroke [1.4% vs 1.4%, RR (95% CI): 1.02 (0.76–1.37), P = 0.881], or death [0.4% vs 0.3%, RR (95% CI): 1.14 (0.64–2.02), P = 0.662]. Compared to CEA, TCAR was associated with lower rates of in-hospital myocardial infarction [0.5% vs 0.9%, RR (95% CI): 0.53 (0.35–0.83), P = 0.005], cranial nerve injury [0.4% vs 2.7%, RR (95% CI): 0.14 (0.08–0.23), P < 0.001], and post-procedural hypertension [13% vs 18.8%, RR (95% CI): 0.69 (0.63–0.76), P < 0.001]. They were also less likely to stay in the hospital for more than 1 day [26.4% vs 30.1%, RR (95% CI): 0.88 (0.82–0.94), P < 0.001]. No significant interaction was observed between procedure and symptomatic status in predicting postoperative outcomes. At 1 year, the incidence of ipsilateral stroke or death was similar between the 2 groups [HR (95% CI): 1.09 (0.87–1.36), P = 0.44]. Conclusions: This propensity-score matched analysis demonstrated significant reduction in the risk of postoperative myocardial infarction and cranial nerve injury after TCAR compared to CEA, with no differences in the rates of stroke/death. [ABSTRACT FROM AUTHOR]

Background and Purpose: Delayed intraparenchymal hemorrhages (DIPHs) are one of the most serious complications of cerebral aneurysm treatment with flow diverters (FD), yet their causes are largely unknown. This study analyzes distal hemodynamic alterations induced by the treatment of intracranial aneurysms with FDs. Methods: A realistic model of the brain arterial network was constructed from MRA images and extended with a constrained constructive optimization technique down to vessel diameters of approximately 50μm. Different variants of the circle of Willis were created by alternatively occluding communicating arteries. Collateral vessels connecting different arterial trees were then added to the model, and a distributed lumped parameter approach was used to model the pulsatile blood flow in the arterial network. The treatment of an ICA aneurysm was modeled by changing the local resistance, flow inertia, and compliance of the aneurysmal segment. Results: The maximum relative change in distal pressure induced by the aneurysm treatment was below 1%. However, for certain combinations of the circle of Willis and distal collateralization, important flow reversals (with a wall shear stress larger than approximately 1.0 dyne/cm2) were observed in collateral vessels, both ipsilaterally and contralaterally to the treated aneurysm. Conclusion: This study suggests the hypothesis that flow diverters treatment of intracranial aneurysms could cause important flow reversal in distal collaterals. Flow reversal has previously been shown to be pro-inflammatory and proatherogenic and could therefore have a detrimental effect on these collateral vessels, and thus could be a suitable explanation of DIPHs, while the small distal pressure increase is not. [ABSTRACT FROM AUTHOR]

We present the novel application of transcarotid artery revascularization (TCAR) in two high-risk patients with high-grade internal artery stenosis and concomitant atherosclerotic extracranial carotid artery aneurysms (ECAAs). ECAAs account for

In the past, several experimental investigations aiming at characterizing the natural circulation (NC) behavior in test facilities were carried out. They showed a variety of flow patterns characterized by an inverted U-shape of the NC flow curve versus primary mass inventory. On the other hand, attempts to reproduce such curves using thermal-hydraulic system codes, showed 10–30% differences between the measured and calculated NC mass flow rate. Actually, the used computer codes are generally based upon nodalization using single U-tube representation. Such model may not allow getting accurate simulation of most of the NC phenomena occurring during such tests (like flow redistribution and flow reversal in some SG U-tubes). Simulations based on multi-U-tubes model, showed better agreement with the overall behavior, but remain unable to predict NC phenomena taking place in the steam generator (SG) during the experiment.In the current study, the CATHARE code is considered in order to assess a NC characterization test performed in the four loops PKL facility. For this purpose, four different SG nodalizations including, single and multi-U-tubes, 1D and 3D SG inlet/outlet zones are considered. In general, it is shown that the 1D and 3D models exhibit similar prediction results up to a certain point of the rising part of the inverted U-shape of the NC flow curve. After that, the results bifurcate with, on the one hand, a tendency of the 1D models to over-predict the measured NC mass flow rate and on the other hand, a tendency of the 3D models to under-predict the NC flow rate.

Background and Purpose: Delayed intraparenchymal hemorrhages (DIPHs) are one of the most serious complications of cerebral aneurysm treatment with flow diverters (FD), yet their causes are largely unknown. This study analyzes distal hemodynamic alterations induced by the treatment of intracranial aneurysms with FDs.Methods: A realistic model of the brain arterial network was constructed from MRA images and extended with a constrained constructive optimization technique down to vessel diameters of approximately 50μm. Different variants of the circle of Willis were created by alternatively occluding communicating arteries. Collateral vessels connecting different arterial trees were then added to the model, and a distributed lumped parameter approach was used to model the pulsatile blood flow in the arterial network. The treatment of an ICA aneurysm was modeled by changing the local resistance, flow inertia, and compliance of the aneurysmal segment.Results: The maximum relative change in distal pressure induced by the aneurysm treatment was below 1%. However, for certain combinations of the circle of Willis and distal collateralization, important flow reversals (with a wall shear stress larger than approximately 1.0 dyne/cm2) were observed in collateral vessels, both ipsilaterally and contralaterally to the treated aneurysm.Conclusion: This study suggests the hypothesis that flow diverters treatment of intracranial aneurysms could cause important flow reversal in distal collaterals. Flow reversal has previously been shown to be pro-inflammatory and pro-atherogenic and could therefore have a detrimental effect on these collateral vessels, and thus could be a suitable explanation of DIPHs, while the small distal pressure increase is not.

The repair of tandem carotid lesions has been described using myriad methods, often involving a hybrid approach of stenting with carotid endarterectomy. Because of the worrisome stroke rates associated with this method, we have reported an innovative technique of transcarotid artery revascularization (TCAR) for tandem lesions in a patient with high-grade stenosis of the right common and internal carotid arteries. Technical success was achieved with TCAR via retrograde and antegrade access using dynamic flow reversal for the treatment of both lesions. The patient experienced no postoperative complications, highlighting the successful repair of tandem carotid lesions using TCAR in a patient who is too high risk for carotid endarterectomy.

In this video, we demonstrate our technique for transfemoral carotid artery stenting (CAS) with flow-reversal through a Walrus balloon guide catheter (BGC) using robotic transcranial Doppler (rTCD) monitoring. Before crossing the plaque for distal filter placement and/or angioplasty, the BGC is inflated and the three-way stopcock opened, allowing back-bleeding. Immediately, the rTCD shows a change in blood-flow direction, indicating flow-reversal, which likely occurs due to a passive pressure gradient between the intracranial compartment and the atmospheric pressure. Then, the filter is placed with reduced risk of displacing plaque fragments, and angioplasty and stenting are performed with dual protection afforded by the BGC and filter. This technique may confer greater safety for CAS. Although in this case rTCD was used for proof of concept, it could also be used as a tool to monitor embolic load during CAS procedures. [ABSTRACT FROM AUTHOR]

The commencement of the flow reversal phenomenon is investigated which occurs in the daughter branch of a vertical T‐channel for the flow of Bingham plastic fluids. The combined influences of the imposed forced flow and buoyancy‐driven flow are analyzed at low Reynolds numbers. The mixed convection flow of a Bingham model fluid is explored for a wide range of conditions in terms of Prandtl number, Richardson number, and Bingham number. The critical Richardson number is strongly influenced by the Prandtl number and the yield stress of the Bingham fluids. The dimensionless pressure is seen to decrease with the critical Richardson number. Also, the fractional flow passing through the main branch exhibits a strong direct dependence on the Richardson number while an opposite relationship with Bingham and Prandtl number is observed. [ABSTRACT FROM AUTHOR]

Alternating crossflow filtration is an emerging technology to mitigate fouling in crossflow microfiltration of cell-protein mixtures by periodically reversing the direction of flow. So far, it is understood that the anti-fouling effects are mostly related to the pressure fluctuations upon changing from forward to reversed flow direction and to a smaller extent to the flow reversal along the membrane as such. However, it is not yet clear how pressure fluctuations and flow reversal influence the axial distribution of fouling and the prevailing types of fouling. We conducted alternating crossflow filtrations of a model suspension containing yeast cells (4.2% dry matter) and bovine serum albumin (0.8 g l−1), where the duration and crossflow velocity of the forward and the backwards phase were varied independently. We found that the material, which deposits in the forward phase, can be better removed or loosened during the backwards phase, and vice versa, if forward and backwards flow conditions are equal in terms of time, crossflow velocity and overall transmembrane pressure. This leads to a detectable overall lower resistance due to deposit layer formation. Despite the positive effects of alternating crossflow filtration on filtration resistance, flux, and solute transmission, the less compact deposit layer also allows for an easier penetration of solutes and small particles into the membrane pores, which was detectable in terms of an increased ratio of irreversible fouling resistance. [ABSTRACT FROM AUTHOR]