Search

Introduction: Measurement of biomarkers early after acute myocardial infarction (AMI) might provide a cost-effective and widely available tool to assess infarct severity, myocardial dysfunction, and clinical outcomes. We aimed to induce AMI in miniature pigs, measure the levels of serum biomarkers and global LV function dynamically and explore the release kinetics and optimal sampling time points of copeptin and its correlation with global LV function. Methods: We induced AMI in the experimental group using a closed-chest model. Left ventricular (LV) function was detected by dual-source computed tomography (DSCT) and serum copeptin was determined by ELISA. Results: The serum copeptin levels were increased at 1 hour, peaked at 3 hours, gradually decreased after 6 hours, and returned to baseline 3 days after AMI. At 3 to 6 hours, the copeptin cutoff of 16.97 to 17.44 pmol/l had 100% sensitivity and 100% specificity ( P ⩽ .001) for AMI. Serum copeptin levels at 3 hours and 3 days were negatively correlated with the 3-hours LVEF ( P ⩽ .001), respectively. Conclusion: Serum copeptin levels change in time, and measurements at 3 to 6 hours after AMI had the highest predictive value.

Under high-temperature conditions, supercritical carbon dioxide (S-CO2) power conversion systems have significant advantages, which show great potential in improving energy utilization efficiency, reducing environmental pollution, and realizing sustainable energy development. S-CO2, as a high-efficiency working fluid, can achieve high efficiency in higher temperature thermodynamic cycles, which helps to reduce fuel consumption and greenhouse gas emissions. Since the S-CO2 power cycle is significant to energy conversion and utilization, many researchers have conducted experimental studies on the convective heat transfer characteristics of S-CO2. However, existing studies mainly focus on low-temperature condition (10-200 ℃), and experimental data under hightemperature condition (200-500 ℃) are scarce. Most of the research conditions on the heat transfer characteristics of S-CO2 have not reached the optimal temperature range of the S-CO2 power conversion system, in order to master the critical data of the relevant design, it is necessary to carry out experimental research on the heat transfer characteristics of S-CO2 under high heat flux conditions, which holds a crucial significance in the development of associated power conversion systems. This paper first introduced the construction process of the S-CO2 forced circulation test bench, and evaluated the uncertainty of the relevant experimental data. The main temperature range of the experiment is 450-800 K, the pressure range is 7.40-10.22 MPa, and the heat flux range is 20-1 000 kW/m2. The heat transfer characteristics of S-CO2 in a vertical tube under high-temperature conditions were studied experimentally, and the effects of thermal acceleration and buoyancy on heat transfer were analyzed. The results show that the heat transfer trend of S-CO2 is similar to that of gaseous CO2 under high-temperature conditions, but the values are quite different, and the influence of thermal acceleration and buoyancy effect on the heat transfer of high-temperature S-CO2 is negligible. Finally, in order to develop a reliable prediction method of S-CO2 convection heat transfer under high-temperature conditions, this paper collected the empirical correlations of S-CO2 heat transfer in vertical heating circular tubes commonly found in the literature, and analyzed them under high heat flux, evaluated and analyzed their experimental prediction high-temperature conditions. It is found that there are some differences with the existing experimental data. Therefore, this paper proposes an empirical correlation suitable for high-temperature S-CO2 heat transfer. The newly proposed heat transfer correlation has the highest calculation accuracy, which calculates 96.65% of experimental data within ±10% error. It can achieve higher accuracy, which meets the actual engineering needs.