Search

A concrete-faced sand-gravel dam (CFSGD) is likely to experience a dam breaching accident once there is leakage through the concrete face slab joints or overtopping of the dam. This study aimed to examine the physical process of a CFSGD overtopping breach and considered the influence of the failure of the vertical joint water barrier. The similarity criterion of the model test was deduced and the face slab that met the requirements of the model test was prepared. Through flume model tests, the process of overtopping dam breach was divided into four stages, i.e. Stage I, seepage erosion stage, Stage II, gradual erosion stage, Stage III, violent dam breach stage and Stage IV gradual stabilisation stage. The results showed that under the influence of seepage erosion, the initial breach of the dam occurred at the upper edge of the seepage surface of the downstream slope. The flow process line of the breach was of a 'lean and high' type, and there was a clear increase in the average rate of undercutting and horizontal expansion of the breach, highlighting the important influence of the early seepage erosion stage on the later dam breach process. [ABSTRACT FROM AUTHOR]

Background: Blood pressure is a critical therapeutic goal in intensive care unit (ICU). One important factor influencing blood pressure are analgesia and sedation. Analgesic and sedative drugs are commonly used in critically ill patients. These drugs affect blood pressure by reducing the tension of the venous system, the cardiac preload, and cardiac output and inhibiting cardiac functions. Consequently, vasoactive agents are commonly used to increase blood pressure. The indications for the usage of vasoactive agents are unequivocal. However, opinions on when to stop raising blood pressure vary. This study explored the relationship between blood pressure and sedation., Methods: Patients in the Multiparameter Intelligent Monitoring in Intensive Care-III (MIMIC) database who had received mechanical ventilation, had been administered sedative analgesics during their ICU stay, and met the inclusion criteria were included in this study. The mean arterial pressure (MAP) tendency patterns were identified using spectral clustering and visualized using the t-distributed Stochastic Neighbor Embedding (t-SNE) algorithm. The 28-day mortality rates of patients with different MAP patterns during their first 24 hours in the ICU and their sedation levels were calculated in the crosstab., Results: Fourteen thousand seven hundred and eighty-five patients from the MIMIC-III database were included in this study. Three MAP patterns were identified by spectral clustering. The median MAP of the low, moderate, and high MAP groups was 71.2, 80.4, and 97.6 mmHg, respectively. The 28-day mortality rate of patients in the moderate MAP group (13.0%) was lower than that of patients in the low (16.6%) and high (15.6%) MAP groups. No difference was found in the 28-day mortality rate between the low and high MAP groups. Dynamic changes in blood pressure at different sedation depths were also examined. Notably, compared with light and moderate sedation level, patients in the deep sedation group, especially those in the high MAP group (48.5%), had a higher 28-day mortality rate (36.5%)., Conclusions: Low MAP in the first 24 hours in ICU indicates a high possibility of poor prognosis for critically ill patients on mechanical ventilation. For patients under deep sedation, maintaining a high mean arterial pressure also indicates poor prognosis. A personalized MAP target should be determined according to the severity of illness and level of sedation for each patient., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://dx.doi.org/10.21037/atm-21-2806). The authors have no conflicts of interest to declare., (2021 Annals of Translational Medicine. All rights reserved.)