Abstract: Cell viability is a critical indicator for assessing culture quality in microalgae cultivation for biorefinery and bioremediation. Fluorescent dyes that distinguish viable from nonviable cells can enable viability quantification based on the percentage of live cells. However, fluorescence analysis using the typical flow cytometry method is costly and impractical for industrial applications. To address this, we developed new microplate assays utilizing fluorescein diacetate as a live cell stain and erythrosine B as a dead cell stain. These assays provide a low-cost, simple, and reliable method of assessing cell viability. The proposed microplate assays were successfully applied to monitor the viability of the microalgae Dunaliella viridis under carbon and nitrogen limitation stresses and demonstrated good agreement with flow cytometry measurements. We conducted a systematic investigation of the effects of dye concentration, incubation time, and background fluorescence on the microplate assays' performance. Further, we provide a comprehensive review of commonly used fluorescent dyes for microalgae staining, discuss strategies to enhance assay performance, and offer recommendations for dye selection and protocol development. This study presents a comprehensive new method for microplate-based viability analysis, providing valuable insights for future microalgae viability assessments and applications.

Abstract: Aero-engine is one of the most complex mechanical equipment that can be built by the industry at present. Its complex structure, nonlinear dynamic characteristics and complex and diverse engineering technologies required for normal operation can be called the Mount Everest in the industry. As the power source of aircraft, aero-engine affects the performance, economy and reliability of aircraft, and has important strategic and economic significance. The purpose of this paper is to design the fuel control system for aero-engine starting based on particle swarm optimization. In the experiment, the algorithm of combustion chamber is used to analyze and study the law of steady state fuel control system of aero-engine.

Abstract: The sending-end power systems with high proportion of new energy have insufficient support capacity and poor ability to withstand fault shock. It is urgent to improve the transient stability of sending-end power systems (TSSPS). This paper theoretically analyzes the mechanism of the effect of DC power recovery speed on TSSPS after AC faults at the transmitter side. Firstly, the sending end power system and the DC power recovery process were modelled. Secondly, the direction of oscillation of the relative rotor angle is discussed, which is caused by the AC faults at the transmitter side. Then, the DC power flow model is established, and the analytical expression of the relative power angle with respect to the DC power is derived theoretically, thus the impact mechanism of the power recovery speed on the TSSPS is revealed. Finally, the correctness of the presented impact mechanism is validated using the AC/DC asynchronous interconnection test power system.

Abstract: To the Editor – Right ventricular failure (RVF) is a dreaded complication of durable left ventricular assist device (LVAD) therapy as it causes significant morbidity and mortality. It can be seen in 9-42% of patients following device activation. 1 Thus, identifying cases of subclinical RVF early in the postoperative course is crucial in promptly initiating RVF mitigating strategies. Pulmonary artery pulsatility index (PAPi) has previously been demonstrated to provide real-time quantification of right ventricular (RV) systolic performance and has further demonstrated utility in risk-stratifying LVAD recipients for RVF. 2 However, data on PAPi use for detecting RVF after LVAD initiation is limited. In this issue of the Journal, Wei et al. presented a single-center retrospective analysis of 67 durable LVAD recipients, who had PAPi measured hourly for up to 48 hours postoperatively to examine whether the average PAPi acquired during this time predicted RVF following LVAD implantation. 3 30% of the patients developed RVF, and these patients had a lower median postoperative PAPi than those who did not (1.31 vs 1.82, p=0.01). 3 The authors also constructed a receiver operator curve and identified 1.56 as the optimal cutoff for postoperative PAPi with a sensitivity of 0.70 and specificity of 0.68. 3 We applaud the authors for furthering the evidence on PAPi as a valuable tool in the LVAD population, which until now has focused on its role in preoperative risk stratification for RVF. While postoperative PAPi by its very nature cannot retrospectively inform pre-LVAD risk of RVF, it does have potential value in prognosticating RV performance post-LVAD. This can improve outcomes in those previously deemed low risk for developing RVF by steering rapid treatment with inotropes, inhaled pulmonary vasodilators, or mechanical circulatory support in those patients with low postoperative PAPi. Interestingly, the authors found no correlation between preoperative and postoperative PAPi. More puzzling is that the preoperative PAPi of the patients who developed RVF was higher than those who did not develop RVF (2.35 vs 2.14), which is inconsistent with the >30 studies examining preoperative PAPi as a predictor of RVF after LVAD implantation. 4 Our group published a meta-analysis of these studies and determined a preoperative PAPi <2.17 was predictive of RVF after LVAD implantation. 4 PAPi is a dynamic parameter and is dependent on changes to patients’ clinical states or medical therapy, so it is logical that a “normal” PAPi maybe lower postoperatively given the effects of general anesthesia, physiological stress of surgery, dynamic fluid shifts, active inotrope/vasopressor therapy, and LVAD pump speed settings. The study by Gudejko et al., which was not included in our meta-analysis, demonstrated that PAPi obtained intraoperatively immediately after chest closure as low as 1.5 was not associated with RVF. 5 This illustrates that postoperative PAPi must be interpreted in the context of many variables composing a patient's clinical status at a given time. We would also caution against viewing postoperative PAPi as a risk stratification tool like the Michigan and EUROMACS scores or even preoperative PAPi. One of the goals of identifying patients at increased risk for RVF is to guide LVAD candidacy and preoperative optimization of a patient's clinical status. To improve outcomes, patients at high risk for RVF should not have an LVAD implanted in the first place. However, we may be poorly managing low-risk patients by administering excessive fluids, hypoventilating them, providing inadequate inotropic support, or utilizing high pump speeds, resulting in RV deformation and dysfunction. In this regard, there may be great value in tracking PAPi postoperatively to correlate RV function with postoperative management. The authors’ discovery may have an important role in post-LVAD patient care, but these findings need to be validated with larger prospective studies. 1Turner KR. Right Ventricular Failure After Left Ventricular Assist Device Placement—The Beginning of the End or Just Another Challenge? J Cardiothorac Vasc Anesth. 2019;33:1105-1121.2Kang G, Ha R, Banerjee D. Pulmonary artery pulsatility index predicts right ventricular failure after left ventricular assist device implantation. J Heart Lung Transplant. 2016;35:67-73.3Wei J, Franke J, Kee A, Dukes R, Leonardo V, Flynn BC. Postoperative Pulmonary Artery Pulsatility Index Improves Prediction of Right Ventricular Failure after Left Ventricular Assist Device Implantation. J Cardiothorac Vasc Anesth. 2023. In press.4Essandoh M, Kumar N, Hussain N, et al. Pulmonary artery pulsatility index as a predictor of right ventricular failure in left ventricular assist device recipients: A systematic review. J Heart Lung Transplant. Aug 2022;41:1114-1123.5Gudejko MD, Gebhardt BR, Zahedi F, et al. Intraoperative hemodynamic and echocardiographic measurements associated with severe right ventricular failure after left ventricular assist device implantation. Anesth Analg. 2019;128:25-32. The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Abstract: UN-U3Si2 composite fuel is a promising candidate of Accident Tolerant Fuels (ATFs). Its in-pile creep performance will have an important impact on the irradiation-induced thermo-mechanical coupling behavior and safety of fuel elements. Based on the existing mechanism-based creep models of UN and U3Si2, the finite element analysis was performed for the multi-scale creep behaviors of various UN-U3Si2 composite fuels, and the influences of the U3Si2 volume fraction, applied stress, temperature, fission rate, and grain size were investigated. The dominant creep mechanisms under different conditions were proposed, and the mechanism-based macroscopic creep rate model for the UN-U3Si2 composite fuels were correspondingly developed, quantitatively correlating with the macroscopic creep rate with the U3Si2 vol fraction, temperature, fission rate and equivalent stress. The creep rate predictions obtained by this model were in good agreement with the results of the finite element simulation. The research results indicate that: (1) the irradiation or thermal diffusion creep contributions from the UN and U3Si2 phases were dominated under various conditions; (2) the dislocation creep contributions from the dispersed-phase of U3Si2 were appreciable at the temperatures ranged from 500 K to 1300 K, while those of the matrix-phase of UN appeared only at an extremely high temperature of 1300 K; (3) different from the ordinary inert-matrix dispersion fuels, the macroscopic creep rates of UN-U3Si2 composite fuels were predicted to be almost independent of burnup, due to the slight difference in the irradiation swelling of UN and U3Si2; (4) the total creep contribution proportions of the U3Si2 or UN phase were almost equal to the initial volume fractions, while the creep contribution ratios within the UN or U3Si2 phase vary under different conditions. The evolutions of various creep contributions with the fission density were attributed to the fuel-swelling induced additional stresses.