Inflow Time Research Articles

Data-driven forecasting framework for daily reservoir inflow time series considering the flood peaks based on multi-head attention mechanism

Accurate and reliable daily reservoir inflow forecast plays an essential role in several applications involving the management and planning of water resources, such as hydroelectric generation, flood control, water supply, and basin ecological dispatching. Runoff usually exhibits strong non-linearity, high uncertainty, and spatial and temporal variability. Existing techniques fail to capture complete dynamics change processes effectively. A data-driven forecasting framework for daily reservoir inflow time series considering the flood peaks based on a multi-head attention mechanism was developed, referred to as the GWOCS-VMD-CNN-Transformer (GCVCT). First, the model utilize Grey Wolf Optimizer coupled with Cuckoo Search (GWO-CS) algorithms to optimize parameters in variational mode decomposition model (VMD). This approach helps obtain highly correlated intrinsic mode function (IMF) components, enhancing the frequency resolution of the input dataset. The proposed method overcomes the bottleneck of other available methods by decomposing the time series to capture the main long-term and short-term properties of hydrological processes. Second, the convolution neural network and Transformer (CNN-Transformer) are based on a multi-head attention mechanism as the objective predictive method. Finally, six evaluation indicators verify the performance of the proposed approach. The approach’s reliability was evaluated using the historical daily reservoir inflow data from the Xiluodu (XLD) and Wudongde (WDD) reservoirs in the Jinsha River Basin, China. Several single and hybrid models were developed for comparative analysis. The results indicate that the proposed ensemble approach fits better than other developed model methods. The GCVCT model showed excellent performance in forecasting the inflows of XLD and WDD reservoirs, with NSE values of 0.985 and 0.984, respectively. Furthermore, the GCVCT framework forecast capacity for peak inflow was further verified through discussion and analysis of the 48 peak flows during the validation period, consistently outperforming other models in predicting peak flow for both study reservoirs. This framework provides an effective method for the scientific optimal scheduling of hydropower reservoirs, enabling more sustainable and efficient management practices. It also demonstrates the potential of powerful deep-learning models in intelligent hydrological forecasting.

Designing Effective Low-Impact Developments for a Changing Climate: A HYDRUS-Based Vadose Zone Modeling Approach

Low-Impact Developments (LIDs), like green roofs and bioretention cells, are vital for managing stormwater and reducing pollution. Amidst climate change, assessing both current and future LID systems is crucial. This study utilizes variably saturated flow modeling with the HYDRUS software (version 4.17) to analyze ten locations in Ontario, Canada, focusing on Toronto. Historical and projected climate data are used in flow modeling to assess long-term impacts. Future predicted storms, representing extreme precipitation events, derived from a regional climate model, were also used in the flow modeling. This enabled a comprehensive evaluation of LID performance under an evolving climate. A robust methodology is developed to analyze LID designs, exploring parameters like water inflow volumes, peak intensity, time delays, runoff dynamics, and ponding patterns. The findings indicate potential declines in LID performance attributed to rising water volumes, resulting in notable changes in infiltration for green roofs (100%) and bioretention facilities (50%) compared to historical conditions. Future climate predicted storms indicate reduced peak reductions and shorter time delays for green roofs, posing risks of flooding and erosion. Anticipated extreme precipitation is projected to increase ponding depths in bioretention facilities, resulting in untreated stormwater overflow and prolonged ponding times exceeding baseline conditions by up to 13 h at numerous Ontario locations.

Value of fetal echocardiographic examination in pregnancies complicated by preterm premature rupture of membranes.

Cardiopulmonary and infectious complications are more common in preterm newborns after preterm premature rupture of membranes (pPROM). Fetal echocardiography may be helpful in predicting neonatal condition. Our aim was to assess the cardiovascular changes in fetuses from pregnancies complicated by pPROM and possible utility in predicting the intrauterine or neonatal infection, and neonatal heart failure (HF). It was a prospective study enrolling 46 women with singleton pregnancies complicated by pPROM between 18+0 and 33+6 weeks of gestation and followed until delivery. 46 women with uncomplicated pregnancies served as a control group. Fetal echocardiographic examinations with the assessment of cardiac structure and function (including pulmonary circulation) were performed in all patients. Mean gestational age of pPROM patients was 26 weeks. Parameters suggesting impaired cardiac function in fetuses from pPROM were: higher right ventricle Tei index (0.48 vs. 0.42 p<0.001), lower blood flow velocity in Ao z-score (0.14 vs. 0.84 p=0.005), lower cardiovascular profile score (CVPS), higher rate of tricuspid regurgitation (18.2 % vs. 4.4 % p=0.04) and pericardial effusion (32.6 vs. 0 %). Intrauterine infection was diagnosed in 18 patients (39 %). 4 (8.7 %) newborns met the criteria of early onset sepsis (EOS). HF was diagnosed in 9 newborns. In fetal echocardiographic examination HF group had shorter mitral valve inflow time and higher left ventricle Tei index (0.58 vs. 0.49 p=0.007). Worse cardiac function was observed in fetuses from pPROM compared to fetuses from uncomplicated pregnancies.

Dynamic interaction of inflow and rotor time scales and impact on single turbine wake recovery

The entrainment and recovery of wind turbine wakes are highly dependent on atmospheric inflow conditions, which has typically been quantified through the turbulent intensity. However, recent studies have shown that the integral time scales of the inflow has significant impact on the wake recovery. Concurrently, increased power production can also be achieved through intentionally introducing beneficial time scales by altering the control of the individual wind turbines. This study studies the combined impact of the dynamic interaction between dominant inflow and rotor time scales. The results show increased power production of a downstream wind turbine of more than 50% for the largest thrust coefficients and tip-speed ratios (TSR). However, the peak power gain occurs at different downstream positions indicating that combinations of inflow time scales and TSR = 6 result in faster near wake breakdown compared to the same inflow time scales combined with higher thrust coefficient of TSR = 8.

Temporal changes in the microplankton community due to Kuroshio branch current inflow

Inflow from the Kuroshio Current into coastal areas stimulates biological production. However, to date there are no detailed reports on its temporal changes. In the target area of this study, Kagoshima Bay, Japan, the time of inflow of the Kuroshio branch current can be identified a posteriori based on water temperature data. This study aimed to determine the relationship between the Kuroshio branch current inflow from the surface layer and phytoplankton bloom at the mouth of the bay during the mixing season. Therefore, we compiled data from ship observations in the Kagoshima Bay from 2016 to 2019 to examine changes in water quality (temperature, salinity, and nutrients), microphytoplankton, and microzooplankton versus time since current inflow. In this study, significant relationships were obtained for microplankton in terms of both biomass and cell abundance, and specific growth rates (0.060–0.079 d–1) comparable to that of chlorophyll a. In addition, the current inflow provided nutrients to the surface in the absence of strong wind and waves. Over time, phytoplankton, mostly athecate dinoflagellates, as well as microzooplankton, mainly naked ciliates, proliferated and were quickly preyed upon by mesozooplankton. Over the study period, such events could be observed once every two weeks in most years, suggesting that these frequent phytoplankton blooms support the high biomass of mesozooplankton and larval fish found in this area.

Determinants and effects of microvascular obstruction on serial change in left ventricular diastolic function after reperfused acute myocardial infarction.

Although left ventricular (LV) diastolic dysfunction is more related to functional capacity after acute myocardial infarction (AMI), the determinants of LV diastolic functional change after reperfused AMI remain unknown. This study aimed to investigate the effects of microvascular obstruction (MVO) on mid-term changes in LV diastolic function after reperfused AMI. In a cohort of 72 AMI patients who underwent successful revascularization, echocardiography and cardiovascular magnetic resonance imaging were repeated at 9-month intervals. The late gadolinium enhancement (LGE) amount, segmental extracellular volume fraction, global LV, and left atrial (LA) phasic functions, along with mitral inflow and tissue Doppler measurements, were repeated. Among the included patients, 31 (43%) patients had MVO. During the 9-month interval, LV ejection fraction (EF) and LV global longitudinal strain (GLS) were significantly improved in accordance with a decrease in LGE amount (from 18.2 to 10.3 g, p < 0.001) and LV mass. The deceleration time (DT) of early mitral inflow (188.6 ms-226.3 ms, p < 0.001) and LV elastance index (Ed; 0.133 1/ml-0.127 1/ml, p = 0.049) were significantly improved, but not in conventional diastolic functional indexes. Their improvements occurred in both groups; however, the degree was less prominent in patients with MVO. The degree of decrease in LGE amount and increase in LVEF was significantly correlated with improvement in LV-Ed or LA phasic function, but not with conventional diastolic functional indexes. In patients with reperfused AMI, DT of early mitral inflow, phasic LA function, and LV-Ed were more sensitive diastolic functional indexes. The degree of their improvement was less prominent in patients with MVO.

Interventricular inflow time difference assessed by dual pulsed-wave Doppler echocardiography in dogs with myxomatous mitral valve disease

IntroductionInterventricular inflow time difference (IVID), which is defined as the time interval between the opening of the mitral valve and the opening of the tricuspid valve, hold prognostic value in human patients with heart failure. Few reports regarding IVID are available in dogs. AnimalsNinety dogs with myxomatous mitral valve disease (MMVD) and 47 dogs without heart disease. Dogs with MMVD received unstandardized therapy based on the stage of disease. Materials and methodsThis was a prospective cohort study. Dogs were classified into two groups based on IVID: tricuspid opening preceding mitral opening (TOP) and mitral opening preceding tricuspid opening (MOP). The potential influence of the MOP group at enrollment on the primary outcome (cardiac-related death) was determined by Kaplan–Meier analysis. ResultsAlmost all dogs without heart disease (97.9%) were classified in the TOP group. Twenty-nine dogs (32.2%) were classified in the MOP group. Left heart size, transmitral early diastolic inflow velocity, and right ventricular Tei index were significantly greater in the MOP group compared to those in the TOP group. Cardiac-related death were observed in 34 dogs (40.5%). The dogs in the MOP group at initial examination had shorter survival times than those in the TOP group (586 days vs. >1,831 days; 95% confidence interval, 237–714 days vs. 1,037 days to >1,831 days; P<0.001). ConclusionsInterventricular inflow time difference is potentially useful for prognostic assessments in dogs with MMVD. Further prospective studies that quantify the repeatability and influence of therapy on IVID are needed.

Hydrological modelling of large-scale karst-dominated basin using a grid-based distributed karst hydrological model

Hydrological modelling is important to flood hazard prevention in the flood-prone karst area of Southwest China. Due to the special hydrogeological features with strong spatial heterogeneities and whose information is rarely obtained in large-scale karst-dominated basins; thus, it’s still a challenge to conduct accurate sub-daily distributed precipitation-streamflow simulation in these regions. To reveal the characteristics of hydrological response and the inertia of karst systems that are influenced by the spatial heterogeneity of the degree of karstification, a new Grid-based Distributed Karst Hydrological Model (GDKHM) is developed by this study to simulate streamflow in Li River Basin (LRB), which is a typical large-scale karst-dominated basin of Southwest China. The GDKHM considers the duality of hydrological behavior and the spatial heterogeneities of land uses types and karstification of each grid and river channels routing characteristics between different sub-basins. The results show the GDKHM using calibrated parameters could reflect the spatial distribution characteristics of hydrological response in the LRB. The mean NSE, KGE, R2 and RRE of the streamflow of all the sub-basin outlets during validation period reached 0.82, 0.84, 0.83 and 4.64%, respectively. The hydrograph simulation result of nested interior grid without recalibration was also satisfied. Furthermore, the GDKHM was able to reproduce the Auto-correlation function (ACF) shapes of simulated lateral inflow time series in sub-basins with different percentage of karst terrain areas (PKTAs) during validation period, and the ACF characteristics information including memory effect, slopes of rapid-conduit and slow-matrix flow phases could be captured, which indicates the model can characterize the spatial variability of karst system inertia in large karst basin. Due to the better performance in hydrograph and ACF of streamflow, GDKHM has the potential to successfully support flood forecasting in large-scale karst-dominated basins.

ECOENGINEERING FRESHWATER FLOWS FOR ESTUARY HYDROLOGICAL STATE

The quantity, quality and timing of freshwater inflow into estuaries is critical to support estuarine ecosystem health. However, most estuaries are affected by upstream manipulation of freshwater inflows. Coinciding with the United Nations Decade of Restoration (2021–2030), there is great interest in re-creating functional estuarine ecosystems, including by modifying the physio-chemical characteristics with the premise that a functional ecosystem will follow (ecoengineering). To restore estuarine ecology, the physical processes of the system must first be conductive to supporting the re-establishment and sustenance of biota. These physical processes are generally under-monitored and often not used as a measure of restoration success. We explore ecoengineering to restore freshwater inflows to estuaries, focused on hydrological state. We use the Pressure—State—Response (PSR) framework to set the context for this review.

UISCEmod: Open-source software for modelling water level time series in ephemeral karstic wetlands

Characterizing ephemeral karstic wetlands through hydrological modelling is key for sustainable protection of their ecosystems and to understand and mitigate the impact of flooding events. UISCEmod is a new open-source software for modelling water level time series, focused on ephemeral karstic wetlands, that requires minimal input information. UISCEmod contains both experimental and lumped hydrological models, and the calibration process is automated following a Bayesian approach. The main outputs of UISCEmod include volume, stage, inflow and outflow model time series, calibrated model parameters, and the associated uncertainties. UISCEmod was evaluated at 16 representative sites in Ireland obtaining Nash-Sutcliffe Efficiency (NSE) and Kling-Gupta Efficiency (KGE) above 0.85 for both stage and volume time series for most of the sites, showing its potential for covering the need for a simple, pragmatic, and flexible framework for modelling water levels in ephemeral karstic wetlands with relatively limited input data requirements.

Effects of turbulent inflow time scales on wind turbine wake behavior and recovery

Wind turbines experience a range of turbulent time and length scales related to the atmospheric boundary layer, wakes of upstream turbines, and wind farm effects. This work aims to investigate the impact of turbulent scales on wake behavior and recovery, in isolation from overall turbulence intensity, shear, or buoyancy. Large eddy simulations of a single turbine are conducted using idealized single time scale inflows and full spectra turbulent inflows, varying the predominant time scale in the equivalent Strouhal number range of St=0.04–0.5, while maintaining the same turbulence intensity and flow structures. Under idealized inflows, shorter inflow time scales result in a faster breakdown of tip vortices, while longer scales induce greater wake meandering. For full spectra turbulent inflows, shorter integral time scales result in a shorter near-wake region and enhanced wake recovery, while wake meandering occurs to a similar extent when adjusted for the near-wake breakdown location. A wake-generated turbulence region in the range of St=0.3–0.7 is identified in the streamwise velocity spectra, and inflows that contain more turbulent kinetic energy in this range show a faster redistribution from long inflow scales to smaller wake-generated turbulence and enhanced wake recovery. The improved wake recovery for the shortest integral time scale results in a 9% increase in mean rotor-averaged velocity and 35% increase in power at 12R downstream, compared to the longest integral time scale. Overall, it is shown that inflow turbulent scales have a significant impact on wake recovery, particularly through their impact on the near-wake breakdown.

Effects of COVID-19 Infection in Healthy Subjects on Cardiac Function and Biomarkers of Oxygen Transport, Blood Coagulation and Inflammation.

The manifestations, severity, and mortality of COVID-19 are considered to be associated with the changes in various hematological parameters and in immunity. Associations of immunoglobulin G antibodies against severe acute respiratory syndrome-linked coronavirus (IgG-SARS)-positive status with cardiac function and hematological and biochemical parameters in apparently health subjects are poorly understood. The present cross-sectional study included 307 healthy volunteers (24-69 years of age; 44.8 ± 8.6 years; 80.4% men) and was initiated in 2019 before the COVID-19 pandemic. COVID-19 episodes were confirmed by detection of IgG-SARS against SARS-CoV-2 S1 RBD to reveal 70 IgG-SARS-positive and 237 negative participants. Numerous ultrasound characteristics were assessed by echocardiography, and 15 hematological and biochemical parameters were assayed in the blood. Descriptive and comparative analysis was based on the IgG-SARS status of the participants. The left ventricular mass index, mitral ratio of peak early to late diastolic filling velocity or flow velocity across the mitral valve, and deceleration time of early mitral inflow were decreased (p < 0.05) in IgG-SARS-positive participants versus those in IgG-SARS-negative participants according to multivariate logistic regression analysis. Erythrocyte sedimentation rate and platelet count were slightly increased, and blood hemoglobin was decreased in IgG-SARS-positive participants compared with those in IgG-SARS-negative participants. LV filling, inflammation, blood coagulation, and hemoglobin appear to be influenced by COVID-19 infection in healthy participants. Our observations contribute to the definition of vulnerabilities in the apparently healthy subjects with long COVID-19. These vulnerabilities may be more severe in patients with certain chronic diseases.

Quantitative assessment of gastric ischemic preconditioning on conduit perfusion in esophagectomy: propensity score weighting study.

Gastric ischemic preconditioning prior to esophagectomy has been studied as a method to improve gastric conduit perfusion and reduce anastomotic complications, without conclusive results. The aim of this study is to evaluate the feasibility and safety of gastric ischemic preconditioning in terms of post-operative outcomes and quantitative gastric conduit perfusion. Patients who underwent an esophagectomy with gastric conduit reconstruction between January 2015 and October 2022 at a single high-volume academic center were reviewed. Patient characteristics, surgical approach, post-operative outcomes, and indocyanine green fluorescence angiography data (ingress index for arterial inflow and ingress time for venous outflow, and the distance from the last gastroepiploic branch to the perfusion assessment point) were analyzed. Two propensity score weighting methods were used to investigate whether gastric ischemic preconditioning reduces anastomotic leaks. Multiple linear regression analysis was used to evaluate the conduit perfusion quantitatively. There were 594 esophagectomies with gastric conduit performed, with 41 having a gastric ischemic preconditioning. Among 544 with cervical anastomoses, leaks were seen in 2/30 (6.7%) in the ischemic preconditioning group and 114/514 (22.2%) in the control group (p = 0.041). Gastric ischemic preconditioning significantly reduced anastomotic leaks on both weighting methods (p = 0.037 and 0.047, respectively). Ingress index and time of the gastric conduit with ischemic preconditioning were significantly better than those without preconditioning (p = 0.013 and 0.025, respectively) after removing the effect of the distance from the last gastroepiploic branch to the perfusion assessment point. Gastric ischemic preconditioning results in a statistically significant improvement in conduit perfusion and reduction in post-operative anastomotic leaks.

The impact of using the internal mammary artery as a recipient vessel on medial mastectomy skin flap perfusion in autologous breast reconstruction: An observational study using indocyanine green

The internal mammary artery (IMA) is the preferred recipient vessel for microvascular anastomosis in immediate autologous breast reconstruction following skin-sparing mastectomy (SSM). Although the IMA accounts for approximately 60% of the blood supply to the breast, the exact contribution to the mastectomy skin flap perfusion is unclear. The aim of this observational study was to investigate the impact of using the IMA as a recipient vessel on medial mastectomy skin flap perfusion assessed with indocyanine green angiography (ICGA). This observational study included ten consecutive women who underwent immediate autologous breast reconstructions following SSM. Two intraoperative indocyanine green (ICG) assessments were performed to assess tissue perfusion of the upper and lower part of the medial mastectomy skin flap: the first following the SSM and the second after clamping the IMA. During a 120-second angiography, three additional images were made after 60, 90, and 120s. The ICG inflow time and mean, minimum, and maximum fluorescence intensities (FIs) were obtained. Four unilateral and six bilateral autologous breast reconstructions were included. There was no difference in tissue perfusion when comparing the inflow time (24.1s vs. 23.0s, P=0.348), the mean FI (131.4 vs. 124.0, P=0.126), minimum FI (28.6 vs. 33.4, P=0.086), and maximum FI (253.1 vs. 247.6, P=0.166) before and after clamping the IMA. According to this study, the use of the IMA as a recipient vessel does not reduce medial mastectomy skin flap perfusion in patients undergoing immediate autologous breast reconstructions following SSM.

Updating inflow forecasts using empirical statistical matching for real-time prediction of daily net inflows to Okanagan Lake

Accurate predictions of flow periods are important for decision-making within the Okanagan Lake System. A nonparametric method to predict the hydrograph to achieve a closer match with the timing and volume of reservoir inflows during the dominant flow period (February1 to July 31) in Okanagan Lake was developed in this study. The method employed, Real-Time Statistical Matching (RTSM), uses a combination of information from a changing suite of best-fit historical years, existing forecasts, and recent inflow trends. This included a comparison between the current hydrograph against hydrographs derived from historical inflows based on the predicted volume and pattern of the hydrograph. The RTSM-based approach is hypothesized to improve the ability of hydrological models to predict shifts in the general timing of peak net inflows. This makes the RTSM model more robust to both historic and non-historic conditions. The performance of the RTSM-based predictions was compared to the legacy hydrology model based on average timing of historic flows. Results indicate an improvement in predictive accuracy of 10%, 6%, and 80% for Nash-Sutcliffe Efficiency (NSE), root mean squared error to standard deviation ratio (RSR), and percent bias (PBIAS) respectively, which are three different measures of the accuracy of predictions. Further, the success of the Okanagan Fish/Water Management Tool (FWMT) relies on the water and fish managers that use the tool, which extends beyond the quantitative metrics in this study. The authors’ also discussed how the tool’s utility has changed over time from when it was put into practice. It was learned that in practice, the best use of the model was based on the volume-based prediction with the real-time adjustment.

Fetal pulmonary valvuloplasty for pulmonary atresia with intact ventricular septum: a single-center clinical experience.

Fetal pulmonary valvuloplasty for pulmonary atresia with intact ventricular septum: a single-center clinical experience.

Optimal injection rate and catheter size for brain perfusion computed tomography using non-ionic contrast medium in clinically normal Beagles

To evaluate the effects of contrast medium injection rates and intravenous injection catheter sizes on the time-density curve (TDC) of brain perfusion computed tomography (PCT) images in clinically normal Beagles and provide a reference range for the perfusion parameters for clinical application of PCT in veterinary medicine. 5 healthy, sexually intact male Beagles. All dogs underwent general anesthesia for PCT. Contrast medium (350 mg I/kg) was injected at 3 different injection rates (2, 3, and 4 mL/second) and with 2 sizes of an intravenous catheter (20-gauge and 24-gauge). The rostral cerebral artery and dorsal sagittal sinus were selected as the regions of interest of the TDC. Initiation time of arterial inflow (ta), venous outflow (tv), peak time of arterial enhancement (Tap), and the peak time of venous enhancement (Tvp), were measured, and the difference between Tap and tv (Tap-tv) and between Tap and ta (Tap-ta) was calculated. Both Tap-tv and Tap-ta were significantly (P < .05) shorter at the rate of 3 mL/second than at 2 mL/second with the 24-gauge catheter. However, there was no significant difference according to catheter sizes. Particularly, a 4 mL/second injection rate using a 24-gauge catheter mostly resulted in contrast medium leakage and catheter rupture. At a rate of 3 mL/second and with a 24-gauge catheter ensures optimal image acquisition and stable contrast medium injection in brain PCT for small dogs. PCT may be useful for diagnosing cerebrovascular events and hemodynamic changes in small dogs.

Inflow Scenario Generation for the Ethiopian Hydropower System

In a hydropower system, inflow is an uncertain stochastic process that depends on the meteorology of the reservoir’s location. To properly utilize the stored water in reservoirs, it is necessary to have a good forecast or a historical inflow record. In the absence of these two pieces of information, which is the case in Ethiopia and most African countries, the derivation of the synthetic historical inflow series with the appropriate time resolution will be a solution. This paper presents a method of developing synthetic historical inflow time series and techniques to identify the stochastic process that mimics the behavior of the time series and generates inflow scenarios. The methodology was applied to the Ethiopian power system. The time series were analyzed using statistical methods, and the stochastic process that mimics the inflow patterns in Ethiopia was identified. The Monte Carlo simulation was used to generate sample realizations of random scenarios from the identified stochastic process. Then, three cases of inflow scenarios were tested in a deterministic simulation model of the Ethiopian hydropower system and compared with the actual operation. The results show that the generated inflow scenarios give a realistic output of generation scheduling and reasonable reservoir content based on the actual operation.

Minidisc influence on flow variability in accreting spinning black hole binaries: simulations in full general relativity

ABSTRACT We perform magnetohydrodynamic simulations of accreting, equal-mass binary black holes in full general relativity focusing on the effect of spin and minidiscs on the accretion rate and Poynting luminosity variability. We report on the structure of the minidiscs and periodicities in the mass of the minidiscs, mass accretion rates, and Poynting luminosity. The accretion rate exhibits a quasi-periodic behaviour related to the orbital frequency of the binary in all systems that we study, but the amplitude of this modulation is dependent on the existence of persistent minidiscs. In particular, systems that are found to produce persistent minidiscs have a much weaker modulation of the mass accretion rate, indicating that minidiscs can increase the inflow time of matter on to the black holes, and dampen out the quasi-periodic behaviour. This finding has potential consequences for binaries at greater separations where minidiscs can be much larger and may dampen out the periodicities significantly.

Significant Slowed Cortical Venous Blood Flow in Patients with Acute Ischemic Stroke with Large Vessel Occlusion Suggests Poor Collateral Circulation and Prognosis

To investigate the change of cortical venous flow in acute ischemic stroke patients with large vessel occlusion (LVO-AIS) and its clinical value. Baseline whole-brain 4D-CTA/CTP and clinical data of LVO-AIS and a control group were collected from June 2020 to October 2021. Venous inflow time (VIT), venous peak time (VPT), and venous outflow time (VOT) were analyzed on both sides of patients and normal controls. The VIT/VPT/VOT were statistically described and compared between the patient group and normal controls, then, in patients with different collateral circulation and prognoses. Next, the correlation between cortical venous drainage time and collateral circulation grading was analyzed. Finally, logistic regression analysis was used to explore the relationship between the three venous times and prognosis, and receiver operating characteristic (ROC) curves were plotted to assess the value of delayed cortical venous imaging in predicting prognosis. 149 LVO-AIS and 73 normal controls were collected. VIT, VPT, and VOT were significantly delayed on the affected side in the patient group compared with the healthy side (p<0.05) and the controls (p<0.05); VIT and VPT were also significantly delayed on the healthy side of patients compared with the controls (p<0.05). Delayed VIT and VPT on the affected side in the patient group were more significant in patients with poor collateral circulation (p<0.05), and VIT and VPT on the affected side in the patient group were negatively correlated with arterial collateral scores. VIT and VPT were significantly delayed in both sides of patients in the poor prognosis group compared with the good prognosis group (p<0.05). logistic regression showed that patients' affected VPT, arterial collateral scores, and NIHSS were independent predictors of poor prognosis, with an accuracy of 79.6% in predicting poor prognosis. The affected VPT and NIHSS were independent predictors of poor prognosis for patients presenting within 24 hours, with an accuracy of 79.6% in predicting poor prognosis. Cortical venous flow was significantly slowed in both sides of LVO-AIS patients. delayed ipsilateral VPT in LVO-AIS patients can be used as an imaging indicator to determine poor collateral circulation and predict poor prognosis.