Flow Time Research Articles

Influence of bank slope on sinuosity-driven hyporheic exchange flow and residence time distribution during a dynamic flood event

Abstract. This study uses a reduced-order two-dimensional (2-D) horizontal model to investigate the influence of the riverbank slope on the sinuosity-driven hyporheic exchange process along sloping alluvial riverbanks during a transient flood event. The deformed geometry method (DGM) is applied to quantify the displacement of the sediment–water interface (SWI) along the sloping riverbank during river stage fluctuation. This new modeling approach serves as the initial step focusing on the impact of the bank slope on the hyporheic exchange flux (HEF) and the residence time distribution (RTD) of pore water in the fluvial aquifer for a sinuosity-driven river corridor. Several controlling factors, including sinuosity, alluvial valley slope, river flow advective forcing and duration of flow, are incorporated into the model to investigate the effects of bank slope on aquifers of variable hydraulic transmissivity. Compared to simulations of a vertical riverbank, sloping riverbanks were found to increase the HEF. For sloping riverbanks, the hyporheic zone (HZ) encompasses a larger area and penetrated deeper into the alluvial aquifer, especially in aquifers with smaller transmissivity (i.e., due to increased hydraulic conductivity or reduced specific yield). Furthermore, consideration of sloping banks as compared to a vertical riverbank can lead to both underestimation and overestimation of the pore water travel time. The impact of bank slope on residence time was more pronounced during a flood event for high-transmissivity aquifer conditions, while it had a long-lasting influence after the flood event in lower-transmissivity aquifers. Consequently, the impact of bank slope decreases the travel time of water discharging into the river relative to base flow conditions. These findings highlight the need for (re)consideration of the importance of complex riverbank morphology conceptualization in numerical models when accounting for the HEF and RTD. The results have potential implications for river management and restoration and the management of river and groundwater pollution.

Esophago-gastric junction findings on high resolution impedance manometry in children with esophageal atresia.

Using high resolution impedance manometry (HRIM), this study characterized the esophago-gastric junction (EGJ) dynamics in children with esophageal atresia (EA). Esophageal HRIM was performed in patients with EA aged less than 18 years. Objective motility patterns were analyzed, and EGJ data reported. Controls were pediatric patients without EA undergoing investigations for consideration of fundoplication surgery. Seventy-five patients (M:F = 43:32, median age 1 year 3 months [3 months-17 years 4 months]) completed 133 HRIM studies. The majority (64/75, 85.3%) had EA with distal tracheo-esophageal fistula. Compared with controls, liquid swallows were poorer in patients with EA, as evident by significant differences in distension pressure emptying and bolus flow time (BFT). The integrated relaxation pressure for thin liquid swallows was significantly different between EA types, as well as when comparing patients with EA with and without previous esophageal dilatations. The BFT for solid swallows was significantly different when compared with EA types. We have utilized HRIM in patients with EA to demonstrate abnormalities in their long-term EGJ function. These abnormalities correlate with poorer esophageal compliance and reduced esophageal peristalsis across the EGJ. Understanding the EGJ function in patients with EA will allow us to tailor long-term management to specific patients.

The predictive role of carotid artery flow time for anesthesia-induced hypotension in high-risk elderly patients.

Hypotension induced by general anesthesia is associated with postoperative complications, increased mortality, and morbidity, particularly elderly patients. The aim of this study was to investigate the effectiveness of corrected carotid artery flow time (FTc) for predicting hypotension following anesthesia induction in patients over 65 years old.After faculty ethical committee approval and written informed consent, 138 patients (65 years and older, ASA physical status I-III) who scheduled for elective surgery were included in this study. In the pre-operative anesthesia unit, the carotid artery FTc value was measured by ultrasound and hemodynamic values were recorded. Following anesthesia induction with propofol, hemodynamic data were recorded at 1-minute intervals for 3min. Measurements were terminated prior to endotracheal intubation, as direct laryngoscopy and endotracheal intubation could cause sympathetic stimulation and hemodynamic changes.Hypotension occurred in 52 patients (37.7%). The preoperative FTc value of the patients who developed hypotension was statistically lower (312.5 ms) than the patients who did not (345.0 ms) (p < 0.001). The area under the ROC curve for carotid artery FTc was 0.93 (95% CI for AUC:0.89-0.97; p < 0.001) with an optimal cut-off of value for predicting post-anesthesia hypotension 333 ms, a sensitivity of 90.4% and a specificity of 84.9%. As a result of the multiple logistic regression model, carotid artery FTc emerged as the sole independent risk factor for hypotension following anesthesia induction.Preoperative carotid artery FTc measurement is a simple, bedside, noninvasive, and reliable method for predicting anesthesia-induced hypotension in elderly patients.

Comparison of Met Office regional model soil moisture with COSMOS‐UK field‐scale in situ observations

AbstractThe UK Met Office state‐of‐the‐art, deterministic, convection‐permitting, coupled land‐atmosphere, regional weather forecasting system, known as the UKV or UK Variable resolution model (Tang et al. Meteorological Applications, 2013; 20:417–426), has been operational since 2015. Science updates are regularly made to the UKV land surface data assimilation scheme when those updates improve predictions of screen temperature and humidity, since these quantities have a direct impact on atmospheric states and weather forecasts. Less attention has been paid to whether UKV soil moisture analyses are close to independent, in‐situ soil moisture observations, partly because it is difficult to make meaningful comparisons between 1.5 km2 gridded model outputs and traditional point sensor measurements. Soil moisture is recognized to be important when hydrological forecasts for runoff and rivers are required. This is because soil moisture controls the extent to which rainfall can infiltrate the soil, and the amount of surface runoff affects the timing of peak river flows (Ward &amp; Robinson, Principles of Hydrology. McGraw‐Hill Publishing Company; 2000; Singh et al. Water Resources Research, 2021, 57, e2020WR028827). Gómez et al. (Remote Sensing, 2020; 12:3691) report benefits to river flow forecasts when using soil moisture data assimilation in the UKV system instead of a daily downscaled product from the Met Office global model. The Met Office measures soil temperature and soil moisture at Cardington (Osborne &amp; Weedon, Journal of Hydrometeorology, 2021, 22:279–295); there is no other UK Met Office site at which soil moisture is measured. In this study, we use field‐scale (~200 m radius) soil moisture measurements from the UK Centre for Ecology and Hydrology's (UKCEH's) COSMOS‐UK network to provide independent verification and analysis of UKV soil moisture during summer 2018, an unusually dry period in the United Kingdom. We find that the match to COSMOS‐UK soil moisture observations is generally good, and that changes made to the land data assimilation approach during a recent operational upgrade had a generally beneficial impact on UKV soil moisture analyses under very dry conditions.

Development and validation of a phenomenological model for hydrogen fueled PFI internal combustion engines considering Thermo-Diffusive effects on flame speed propagation

This paper proposes a 1D numerical/experimental study on a single-cylinder research ICE equipped with a hydrogen Port Fuel Injection (PFI) system. The experimental campaign covered tests at the fixed speed of 1500 rpm and different levels of load, from 5 bar to 11 bar IMEP, and of air excess, with a relative air-to-fuel ratio ranging from 1.4 to 4.0. A 0D/1D model of the investigated ICE is developed, including detailed combustion, turbulence, and NOx emission sub-models. In particular, combustion model is based on the fractal approach, k-K-T model is adopted for describing turbulent phenomena and NOx emissions are predicted by the Zeldovich mechanism. A sub-model was developed to assess the influence of Thermo-Diffusive (TD) instabilities on the freely propagating flame speed accounting for equivalence ratio, variable transport coefficients and reaction orders. This evaluation considered the impact of TD instabilities commonly observed in lean premixed hydrogen combustion on the flame front. The engine model calibration process enabled the comparison between numerical predictions and experimental observations, encompassing pressure cycles, burn rate traces, and main engine performance (air flow rate, IMEP, indicated efficiency, and timing of main combustion events). The model replicated the IMEP with an average error of 2.5%, gross indicated efficiency with an average error of 1.6%, main combustion angles with an average error of 3.8 CAD on CA50, and NOx emissions satisfactorily, showing high sensitivity to operational parameters. Nonetheless, less accurate predictions occur in cases with significantly elevated λ values (λ>3.6), which were attributed to the presence of thickened flames, where some assumptions inherent to the adopted combustion model may fail. Finally, a comparison between the proposed approach and the one proposed in Ballerini et al. (2022) is presented, and readers are provided with recommendations for further development of future models that account for Thermo-Diffusive instabilities in lean hydrogen combustion.

Multi‐Criteria Shape Optimization of Flow Fields for Electrochemical Cells

AbstractShape optimization of flow fields for electrochemical cells is performed. Simulation models of the flow field are introduced with and without the porous transport layer. The latter model is less detailed and used for shape optimization whereas the former one is used to validate the obtained results. Three objective functions are proposed based on the uniformity of the flow and residence time as well as the wall shear stress. After considering the respective optimization problems separately, techniques from multi‐criteria optimization are used to treat the conflicting objective functions systematically. The results highlight the potential of this approach for generating novel flow field designs for electrochemical cells.

The time constant of the cerebral arterial bed: exploring age-related implications.

The time constant of the cerebral arterial bed (τ) represents an estimation of the transit time of flow from the point of insonation at the level of the middle cerebral artery to the arteriolar-capillary boundary, during a cardiac cycle. This study assessed differences in τ among healthy volunteers across different age groups.Simultaneous recordings of transcranial Doppler cerebral blood flow velocity (CBFV) and arterial blood pressure (ABP) were performed on two groups: young volunteers (below 30years of age), and older volunteers (above 40years of age). τ was estimated using mathematical transformation of ABP and CBFV pulse waveforms. 77 healthy volunteers [52 in the young group, and 25 in the old group] were included. Pulse amplitude of ABP was higher [16.7 (14.6-19.4) mmHg] in older volunteers as compared to younger ones [12.5 (10.9-14.4) mm Hg; p < 0.001]. CBFV was lower in older volunteers [59 (50-66) cm/s] as compared to younger ones [72 (63-78) cm/s p < 0.001]. τ was longer in the younger volunteers [217 (168-237) ms] as compared to the older volunteers [183 (149-211) ms; p = 0.004]. τ significantly decreased with age (rS = - 0.27; p = 0.018).τ is potentially an integrative marker of the changes occurring in cerebral vasculature, as it encompasses the interplay between changes in compliance and resistance that occur with age.

Value of carotid corrected flow time or changes value of FTc could be more useful in predicting fluid responsiveness in patients undergoing robot-assisted gynecologic surgery: a prospective observational study.

The aim of this study was to evaluate the ability of point-of-care Doppler ultrasound measurements of carotid corrected flow time and its changes induced by volume expansion to predict fluid responsiveness in patients undergoing robot-assisted gynecological surgery. In this prospective study, carotid corrected flow time was measured using Doppler images of the common carotid artery before and after volume expansion. The stroke volume index at each time point was recorded using noninvasive cardiac output monitoring with MostCare. Of the 52 patients enrolled, 26 responded. The areas under the receiver operating characteristic curves of the carotid corrected flow time and changes in carotid corrected flow time induced by volume expansion were 0.82 and 0.67, respectively. Their optimal cut-off values were 357 and 19.5 ms, respectively. Carotid corrected flow time was superior to changes in carotid corrected flow time induced by volume expansion for predicting fluid responsiveness in this population.

The Reliability of Carotid Artery Doppler Ultrasonography Indices in Predicting Fluid Responsiveness during Surgery for Geriatric Patients: A Prospective, Observational Study.

The reliability of determining fluid responsiveness during surgery in geriatric patients is challenging. Our primary outcome was to determine the reliability of Corrected Flow Time (FTc) in predicting fluid responsiveness. Elderly patients undergoing major surgery under general anesthesia were included. Measurements of common carotid artery diameter, velocity time integral, and systolic flow time (FT) were performed before and after a fluid challenge. FTc and carotid blood flow (CBF) were subsequently calculated. The median change in carotid diameter was significantly higher in the fluid-responder (R) compared to the non-responder (NR) (6.51% vs. 0.65%, p = 0.049). The median change in CBF was notably higher in R compared to NR (30.04% vs. 9.72%, p = 0.024). Prior to the fluid challenge, systolic FT was significantly shorter in R than NR (285 ms vs. 315 ms, p = 0.027), but after the fluid challenge, these measurements became comparable among the groups. The change in systolic FT was higher in R (15.38% vs. 7.49%, p = 0.027). FTc and the change in FTc exhibited similarities among the groups at all study time points. Receiver operating characteristic analysis demonstrated an area under the curve of 0.682 (95% CI: 0.509-0.855, p = 0.039) for carotid diameter, 0.710 (95% CI: 0.547-0.872, p = 0.011) for CBF, 0.706 (95% CI: 0.540-0.872, p = 0.015) for systolic FT, and 0.580 (95% CI = 0.389-0.770, p = 0.413) for FTc. In geriatric patients, potential endothelial changes in the carotid artery may influence the dynamic markers of fluid responsiveness. Despite the demonstrated effectiveness of FTc in predicting fluid responsiveness in the general population, this study underscores the limited reliability of carotid Doppler ultrasonography indices for prediction in a geriatric patient population.

Bladder dysfunction in adolescents with type 1 diabetes

It is increasingly significant that adults with diabetes experience lower urinary tract symptoms, however, there has been limited research in younger individuals with type 1 diabetes. To investigate bladder function using non-invasive urodynamics as a potential indicator of autonomic neuropathy in adolescents with type 1 diabetes. This involved examining the association between urinary flow disturbances, reported symptoms, and results from other autonomic tests. Cross-sectional study enrolling 49 adolescents with type 1 diabetes and 18 control subjects. All participants underwent uroflowmetry and ultrasound scanning, completed the Composite Autonomic Symptom Score (COMPASS)-31 questionnaire, and were instructed to record their morning urine volume and voiding frequencies and report them back. Cardiovascular reflex tests (CARTs) and the quantitative sudomotor axon reflex test (QSART) were performed. The main results are shown in the Summary figure. In this study, urological abnormalities were not significantly more frequent in adolescents with diabetes, however, urological issues were observed. This is supported by previous findings of Szabo etal. who found that adolescents with type 1 diabetes had reduced flow acceleration and time to maximum flow compared to control subjects. In our study, we observed cases with reduced acceleration and prolonged uroflow curves, possibly indicating detrusor underactivity. People with diabetes had a higher risk of nocturia than healthy controls, which our results supported. Some adolescents reported urination twice per night. Based on these findings, it is considered beneficial to ask about urological symptoms annually to determine if more examinations (frequency-volume charts and uroflowmetry) are necessary and/or if any opportunities for treatment optimization exist. However, uroflowmetry has limitations, as bladder filling and emptying is a complex process involving multiple pathways and neurological centers, making it difficult to standardize and evaluate. Another limitation of this study was that our control group was smaller and consisted of fewer males than females, which could affect the results due to differences in anatomy and physiology in the lower urinary tract system. In conclusion, adolescents with type 1 diabetes, as well as healthy adolescents, frequently experience urological symptoms. Although urological abnormalities were not significantly more frequent in adolescents with diabetes in this study, the focus on nocturia and risk for bladder dysfunction seems relevant, even in adolescents without any other tests indicating autonomic dysfunction.

Establishment and transfer management of veno-arterial extracorporeal membrane oxygenation in patients with difficult downtime during cardiopulmonary bypass surgery

To investigate the establishment method, coordination points and safe transport management strategy of vena-arterial extracorporeal membrane oxygenation (VA-ECMO) in patients with downtime difficulties during cardiopulmonary bypass (CPB). A observation study was conducted. The patients admitted to the department of critical care medicine of the First Affiliated Hospital of Wannan Medical College (Yijishan Hospital) from January 2020 to October 2022 were enrolled. These patients could not be separated from CPB and received VA-ECMO-assisted CPB surgery. The clinical data of the patients were recorded, including the basic information of the patients, the data of VA-ECMO establishment and transport process, the clinical indicators before and after VA-ECMO installation, the operation data of VA-ECMO and clinical outcomes. The experience was summarized from the aspects of extracorporeal membrane oxygenation (ECMO) establishment, transport process, team cooperation, and adverse events during transport. The clinical indicators before and after ECMO operation were compared. According to whether ECMO was successfully weaned, the patients were divided into a successful weaning group and a failure weaning group, and the clinical data between the two groups were compared. Eighteen patients who underwent VA-ECMO-assisted CPB were enrolled, including 10 males and 8 females. The average age was (56.7±12.3) years old. Preoperative left ventricular ejection fraction (LVEF) was 0.46±0.10, and the main reasons for switching to VA-ECMO assistance included right ventricular systolic weakness in 6 cases, total cardiac systolic weakness in 5 cases, left ventricular systolic weakness in 4 cases, high pulmonary arterial pressure in 2 cases, and intractable ventricular fibrillation in 1 case. Among the 18 patients transferred from CPB to VA-ECMO, 10 cases were successfully weaned and 8 cases failed. In ICU, 8 cases survived, 5 cases died, and 5 cases gave up treatment and discharged. The average time for successful CPB to VA-ECMO establishment was (24.6±7.4) minutes, initial blood flow was (3.3±0.4) L/min, and transit time was (8.4±1.5) minutes. ECMO-assisted duration averaged (82.0±69.3) hours. Adverse events occurred in 9 patients during ECMO establishment and transfer. Post-ECMO onboarding for 4 hours, significant improvements were noted in blood lactic acid (Lac), pH value, mean arterial pressure (MAP), central venous oxygen saturation (ScvO2) as compared with pre-ECMO onboarding [Lac (mmol/L): 10.5±7.0 vs. 15.2±6.8, pH value: 7.38±0.92 vs. 7.26±0.87, MAP (mmHg, 1 mmHg ≈ 0.133 kPa): 74.9±13.7 vs. 58.4±17.0, ScvO2: 0.678±0.065 vs. 0.611±0.061, all P < 0.01], and vasoactive-inotropic score (VIS) was also decreased (39.8±29.8 vs. 68.9±64.4, P < 0.01). Compared with successful weaning group, the patients in the failed weaning group exhibited higher pre-machine Lac (mmol/L: 18.8±7.8 vs. 12.3±4.3, P < 0.05), longer CPB time [minutes: 238.0 (208.8, 351.2) vs. 200.0 (185.8, 217.0), P < 0.05], and shorter ECMO-assisted time [hours: 19.5 (11.0, 58.8) vs. 94.5 (65.8, 179.8), P < 0.01]. However, there was no statistically significant difference in pre-machine pH value, ScvO2, MAP, VIS score, and initial blood flow and establishment time of ECMO between the two groups. VA-ECMO is an effective circulatory aid for CPB surgery that cannot be weaned after CPB. The establishment and transfer of CPB "bridge" to ECMO aid depends on multi-disciplinary treatment (MDT) cooperation. The success rate of ECMO weaning is related to the Lac and CPB duration. If it is not possible to detach from the CPB successfully, VA-ECMO should be initiated as early as possible.

Modeling analysis of pulsatile non-Newtonian blood flow in a renal bifurcated artery with stenosis

A transient transport flow model is adopted in a renal bifurcated artery with different stenosis cases to examine the flow phenomena when the non-Newtonian blood flow regime within the three-dimensional space domain is chosen as a pulsatile nature. The nonlinear governing equations are solved using the Finite Element Method with suitable initial-boundary conditions. During numerical computation, distinct hemodynamic parameters including Wall shear stress, Reynolds number, power law index are evaluated based on different stenosis severities (0%, 25%, and 50%) and stenosis lengths (0mm, 0.5mm, and 1mm). For 0%, 25%, and 50% stenosis, the approximate values of velocity and pressure profiles are estimated at t = 5s at various positions, and achieved the highest velocities that were around 0.07m/s, 0.08m/s, and 0.13m/s respectively. The unsteady response of the stress due to stenosis-induced shear on the outside wall is described as a result of stenosis at t = 0.1s, 0.2s, 5s. The flow is severely restricted by constriction, which increases wall movement and produces stress, depending on the amount of stenosis. As pulsatile flow time increases due to the presence of stenosis, the wall shear stress decreases gradually. The impact of Reynolds numbers on pressure profiles and velocity profiles are displayed for Re = 100, 300, 500, and 700, and found that both velocity and pressure outlines increase significantly. In order to identify the flow phenomena, the influences of the power law index for n = 0.1, 0.3568, 0.5 are presented on the velocity and pressure profiles. Shear-thinning flow occurs for 0<n<1, pseudoplastic flow occurs for n = 0.1 and Bingham plastic flow occurs for n = 0.5. The modeling investigations of blood flow via arteries could assist in the diagnosis and treatment of arterial illnesses; as well as expand the knowledge about cardiovascular physiology and lead the development of revolutionary medical interventions to enhance patient treatment outcomes.

Comparison between processing time for groundwater flow of fractured porous media via analytic element method

The aim of our work is to study two-dimensional fractured flow simulations for groundwater by using non-identical aperture of fractures via Analytic Element Method, and make a comparison between processing time of both techniques i.e. iterative and matrix method. Numerical solutions for the considered problems are totally based on series expansions, whereas the effects of every fracture are expressed as a series which obey Laplace's equation. In all examined cases, it is evident that the iterative method is not able to converge, while by introducing the matrix method, the expected results are obtained with minimum computational cost (processing time).

Toughness behavior and deformation mechanisms in FCC-based Fe45Co30Cr10V10Ni5-xMnx high-entropy alloys: Insights from instrumented Charpy impact tests

This study investigated toughness properties of FCC-based Fe45Co30Cr10V10Ni5-xMnx high entropy alloys (HEAs). Ductile-dimpled rupture mode in all alloys and test temperatures complicated precise explanations on Charpy impact energy, but the instrumented Charpy test provided a breakdown of total energy (ET) into initiation energy (EI) and propagation energy (EP), offering critical insights into Mn-content- and temperature-related energy variations. Pmax and TP, reflecting maximum flow stress and time, respectively, until initiation of crack propagation from the notch tip, involved a transition of deformation mechanisms from slip to TWIP, then to BCC-TRIP, thereby inducing increased strain hardening and delaying plastic instability at the notch tip. At 25 °C, an increase in Mn content prompted a transition in deformation behavior from slip to TWIP and subsequently to BCC-TRIP, correlating well with increased Pmax and TP and consequently ET due to enhanced strain hardenability. At −196 °C, predominant BCC-TRIP activity in all alloys led to increased formation of BCC martensite, intensifying strain hardening and requiring higher Pmax for crack initiation than at 25 °C. Due to minimal slip line field formation associated with reduced plastic deformation, however, cracks initiated directly from the notch-tip center, representing fast initiation of crack propagation and consequently reduction in EI and ET. Thus, utilizing parameters from instrumented Charpy tests, including Pmax, TP, EI, EP, and ET, provided insights into fracture phenomena and their interrelations in the present HEAs.

Exploring the interrelationships between composition, rheology, and compressive strength of self-compacting concrete: An exploration of explainable boosting algorithms

This study introduces a novel methodology for enhancing the compressive strength of self-compacting concrete (SCC) via the use of the Explainable Boosting Machine (EBM), a sophisticated and interpretable machine learning algorithm. It presents a data-driven model that aims to accurately predict the strength of SCC by considering the intricate interactions among its various elements. Additionally, the model provides insights into the variables that influence SCC's compressive strength. By using EBM in conjunction with XGBoost and CatBoost algorithms, this study conducts a comparative examination of predictive abilities using datasets related to composition and rheology. The findings reveal that CatBoost has greater predictive performance using rheology dataset, as shown by an R2 value of 0.977. Conversely, XGBoost exhibits a higher predictive capability using the composition dataset, as indicated by an R2 value of 0.947. The EBM can provide comprehensive explanations at both global and local levels. It effectively identifies the key factors that have a significant influence on compressive strength. These factors include the coarse aggregate content, cement content, water content, viscosity, and V-funnel flow time. The study findings provide more evidence to support the notion that including rheological data into the model leads to a notable improvement in its accuracy. This outcome further confirms the existence of a direct correlation between rheological properties and compressive strength. The explanatory insights provided by EBM give practical instructions for customising SCC mixes to attain desired strengths. This facilitates quality control and enables personalised concrete design in the field of construction. This study highlights the potential of interpretable machine learning algorithms in improving the predictive modelling of SCC features. This advancement may lead to the development of more durable, efficient, and customised building materials.

Numerical study of CO2 trans-critical process inside micromodel based porous structures under supercritical pressures

Understanding the flow, heat transfer, and trans-critical process of carbon dioxide in porous media is crucial for various applications, including CO2 sequestration, soil remediation and oil and gas recovery, due to its unique physical properties in the critical region. In this study, a porous media model on a microfluidic chip structure was simulated to emphasize the heat transfer and trans-critical process of CO2 under supercritical pressure in porous media. The study aims to observe the behaviors of CO2 during its transition from subcritical to supercritical temperature under supercritical pressure. The main objective is to observe the temperature distribution and pressure change of CO2 in a porous media model under the influence of bottom heating. At the same time, we observe the changes in the position of the critical temperature point of CO2 in porous media and analyze its heat exchange process in porous media. After the flow reaches a steady state, the temperature span near the grains is 1.6 K, and the pressure drop per unit length is 1480.3 Pa/mm. As the flow time progresses, the critical temperature line migrates from outlet region to inlet region, the range of sCO2 narrows from 81.7 % to 84.7 % in the porous media region. Finally, the influence of different working conditions on the trans-critical region is studied. It is hoped that this study will contribute to the understanding of the trans-critical process of CO2 in porous media.

Urodynamic insights: exploring the relationship between detrusor overactivity and pelvic organ prolapse in women with urge incontinence.

Pelvic organ prolapse (POP) and overactive bladder (OAB) commonly affect the aging female population. We aimed to investigate the possible relationship between the two, as reflected by urodynamic studies. A retrospective analysis was conducted on women who underwent urodynamic studies at a university-affiliated tertiary medical center from January 2018 to January 2021. Women presenting with urge incontinence and diagnosed with detrusor overactivity (DO) were included in the study. Based on the presence or absence of a modified POP-Q ≥ grade 2, these women were categorized into two groups. Data on general demographics, clinical symptoms, and urodynamic findings were extracted and compared using SPSS. During the study period, 949 urodynamic evaluations were performed. Of these, 303 (31.92%) reported urge incontinence. Out of this subset, 151 (49.83%) were diagnosed with DO. Within this group, 18 (11.9%) had POP, while 134 (88.1%) did not. The POP group had a notably higher incidence of prior vaginal hysterectomy and anterior colporrhaphy (p = 0.02 and p = 0.01, respectively). While most urodynamic parameters were similar between groups, there was a significant increase in hesitancy in the POP group (13s vs 8s, p = 0.03). There was a trend indicating a reduced median Q max (12ml/s vs. 18ml/s, p = 0.06) and an increased flow time (55s vs 40s, p = 0.08) in the POP group. The urodynamic profile of the POP group suggests an obstructive voiding pattern. Further longitudinal research is essential to fully understand the relationship between POP and OAB.

The parametric Willmore flow

Abstract We establish a minimal positive existence time of the parametric Willmore flow for any smooth initial data (smooth immersion of a closed oriented surface). The minimal existence time is a function exclusively of geometric data which in particular are all well defined for general weak Lipschitz W 2 , 2 W^{2,2} immersions. This fact opens in particular the possibility for defining the Willmore flow for weak Lipschitz W 2 , 2 W^{2,2} initial data.

Extracorporeal cardiopulmonary resuscitation for in- and out-of-hospital cardiac arrest: The race against time

ObjectivesExtracorporeal cardiopulmonary resuscitation (ECPR) is increasingly used due to its beneficial outcomes and results compared to conventional CPR. Cardiac arrests can be categorized depending on location: in-hospital cardiac arrest (IHCA) and out-of-hospital cardiac arrest (OHCA). Despite this distinction, studies comparing the two are scarce, especially in comparing outcomes after ECPR. This study compared patient characteristics, cardiac arrest characteristics, and outcomes. MethodsBetween 2016 and 2022, patients who underwent ECPR for cardiac arrest at our institution were retrospectively analyzed, depending on the arrest location: IHCA and OHCA. We compared periprocedural characteristics and used multinomial regression analysis to indicate parameters contributing to a favorable outcome. ResultsA total of n = 157 patients (100%) were analyzed (OHCA = 91; IHCA = 66). Upon admission, OHCA patients were younger (53.2 ± 12.4 vs. 59.2 ± 12.6 years) and predominantly male (91.1% vs. 66.7%, p=<0.001). The low-flow time was significantly shorter in IHCA patients (41.1 ± 27.4 mins) compared to OHCA (63.6 ± 25.1 mins). Despite this significant difference, in-hospital mortality was not significantly different in both groups (IHCA = 72.7% vs. OHCA = 76.9%, p = 0.31). Both groups' survival-to-discharge factors were CPR duration, low flow time, and lactate values upon ECMO initiation. ConclusionSurvival-to-discharge for ECPR in IHCA and OHCA was around 25%, and there was no statistically significant difference between the two cohorts. Factors predicting survival were lower lactate levels before cannulation and lower low-flow time. As such, OHCA patients seem to tolerate longer low-flow times and thus metabolic impairments compared to IHCA patients and may be considered for ECMO cannulation on a broader time span than IHCA.

Prognostic value of arterial carbon dioxide tension during cardiopulmonary resuscitation in out-of-hospital cardiac arrest patients receiving extracorporeal resuscitation

BackgroundCurrent guidelines on extracorporeal cardiopulmonary resuscitation (ECPR) recommend careful patient selection, but precise criteria are lacking. Arterial carbon dioxide tension (PaCO2) has prognostic value in out-of-hospital cardiac arrest (OHCA) patients but has been less studied in patients receiving ECPR. We studied the relationship between PaCO2 during cardiopulmonary resuscitation (CPR) and neurological outcomes of OHCA patients receiving ECPR and tested whether PaCO2 could help ECPR selection.MethodsThis single-centre retrospective study enrolled 152 OHCA patients who received ECPR between January 2012 and December 2020. Favorable neurological outcome (FO) at discharge was the primary outcome. We used multivariable logistic regression to determine the independent variables for FO and generalised additive model (GAM) to determine the relationship between PaCO2 and FO. Subgroup analyses were performed to test discriminative ability of PaCO2 in subgroups of OHCA patients.ResultsMultivariable logistic regression showed that PaCO2 was independently associated with FO after adjusting for other favorable resuscitation characteristics (Odds ratio [OR] 0.23, 95% Confidence Interval [CI] 0.08–0.66, p-value = 0.006). GAM showed a near-linear reverse relationship between PaCO2 and FO. PaCO2 < 70 mmHg was the cutoff point for predicting FO. PaCO2 also had prognostic value in patients with less favorable characteristics, including non-shockable rhythm (OR, 3.78) or low flow time > 60 min (OR, 4.66).ConclusionPaCO2 before ECMO implementation had prognostic value for neurological outcomes in OHCA patients. Patients with PaCO2 < 70 mmHg had higher possibility of FO, even in those with non-shockable rhythm or longer low-flow duration. PaCO2 could serve as an ECPR selection criterion.