This study aimed to investigate the protective effect of angiotensin converting enzyme 2 (ACE2) on lipopolysaccharide (LPS)-induced acute lung injury (ALI). After generating ALI mouse models by ...injecting LPS, the levels of ACE2, inflammatory factors, and downstream proteins of the LPS-TLR4 pathway were analyzed. LPS-challenged BEAS-2B cells were established in vitro. Next, a eukaryotic expression vector, pm-ACE2, was constructed and validated. Challenged cells were transfected with pm-ACE2 containing enhanced green fluorescent protein, or they were treated with D-Ala-Ang-(1-7), angiotensin converting enzyme inhibitor (ACEI), angiotensin receptor blocker (ARB) and the LPS-TLR4 pathway inhibitor dimethyl fumarate (DMF) for analysis of how the above factors contribute to ACE2 regulation. Expression of renin, Ang II, ACE and angiotensin II type 1 receptor (AT1R) was subsequently assessed. In the ALI model, mice exhibited decreased expression of ACE2, lung pathological injury, inflammatory injury, and abnormal activation of the LPS-TLR4 pathway. LPS-challenged BEAS-2B cells demonstrated upregulated expression of renin, Ang II, ACE and AT1R. After injection of ACE2, lung function and lung pathological injury were significantly improved, and that effect was accompanied by attenuated inflammation, and inactivation of the LPS-TLR4 pathway. Cell studies showed similar results. The above observations were further enhanced when there was a combined treatment with DMF and pm-ACE2. D-Ala-Ang-(1-7) treatment attenuated the protective effect of ACE2, while ACEI and ARB treatment alleviated LPS-induced pneumonic injury. In conclusion, ACE2 was expressed at low levels in response to LPS-induced ALI. Overexpression of ACE2 regulates the ACE2/Ang-(1-7)/Mas and ACE/Ang II/AT1 axes to maintain dynamic balance of the renin-angiotensin system, and attenuate inflammatory response.
Recently, the converters controlled by droop controller with phase-locked loop were observed in islanded ac microgrids. However, only the state-space-based approach was applied to investigate the ...stability of this converter in the previous works. Compared with the state-space-based approach, the characteristic equation approach has plenty of advantages, such as convenient stability margin analysis (phase margin, gain margin, etc.) and simple stability criterion (Routh criterion). Thus, a novel small-signal modeling approach based on characteristic equation for converter-dominated ac microgrids is proposed to assess the system low-frequency stability in this paper. First, considering zero-order holder and time delay, the small-signal characteristic equation of this converter is presented by Padé approximation and dynamic phasor model. Furthermore, the implementation and parameter design of the converters are studied under the practical considerations. Compared with the existing characteristic equation methods, the proposed approach can verify that the performance is significantly improved. Eventually, simulations and experimental results are presented, indicating that the proposed approach can assess the system low-frequency stability conveniently and accurately.
The rapid spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has led to the coronavirus disease 2019 (COVID-19) worldwide pandemic. This unprecedented situation has garnered ...worldwide attention. An effective strategy for controlling the COVID-19 pandemic is to develop highly accurate methods for the rapid identification and isolation of SARS-CoV-2 infected patients. Many companies and institutes are therefore striving to develop effective methods for the rapid detection of SARS-CoV-2 ribonucleic acid (RNA), antibodies, antigens, and the virus. In this review, we summarize the structure of the SARS-CoV-2 virus, its genome and gene expression characteristics, and the current progression of SARS-CoV-2 RNA, antibodies, antigens, and virus detection. Further, we discuss the reasons for the observed false-negative and false-positive RNA and antibody detection results in practical clinical applications. Finally, we provide a review of the biosensors which hold promising potential for point-of-care detection of COVID-19 patients. This review thereby provides general guidelines for both scientists in the biosensing research community and for those in the biosensor industry to develop a highly sensitive and accurate point-of-care COVID-19 detection system, which would be of enormous benefit for controlling the current COVID-19 pandemic.
•The viral particles structure, genome and gene expression characteristics of SARS-CoV-2 are described.•The current SARS-CoV-2 viral particles, RNA, antigens, and antibody detection methods are reviewed.•The clinical performance and unmet problems associated with SARS-CoV-2 RNA antigen, and antibody detection are highlighted.•Potential biosensors for use in developing point-of-care, rapid, high-sensitivity SARS-CoV-2 detection methods are discussed.
This paper investigates sampled-data synchronization problem of Markovian coupled neural networks with mode-dependent interval time-varying delays and aperiodic sampling intervals based on an ...enhanced input delay approach. A mode-dependent augmented Lyapunov-Krasovskii functional (LKF) is utilized, which makes the LKF matrices mode-dependent as much as possible. By applying an extended Jensen's integral inequality and Wirtinger's inequality, new delay-dependent synchronization criteria are obtained, which fully utilizes the upper bound on variable sampling interval and the sawtooth structure information of varying input delay. In addition, the desired stochastic sampled-data controllers can be obtained by solving a set of linear matrix inequalities. Finally, two examples are provided to demonstrate the feasibility of the proposed method.
This paper addresses the problem of stability for linear systems with time-varying delay. A novel augmented Lyapunov–Krasovskii functional is constructed by using the idea of optimally dividing the ...delay interval 0,τ(t) into some variable sub-intervals and line integral technology. Using the novel augmented functional, the new delay-dependent stability criteria are proposed for linear systems with time-varying delay. The gain is that this stability criterion can lead to much less conservative stability results compared to other methods for linear systems with delay. Two numerical examples are provided to verify the effectiveness of the proposed criteria.
This paper is concerned with the synchronization problems for an array of neural networks with hybrid coupling and interval time-varying delay. First, a novel augmented Lyapunov-Krasovskii functional ...(LKF) method is proposed to develop delay-dependent synchronization criteria for the networks, which makes use of more relaxed conditions by employing the new type of augmented matrices with Kronecker product operation. The proposed method can handle a multitude of Kronecker product operations in the LKF and alleviates the requirements of the positive definiteness of some conditional matrices which are usually considered in the existing methods for complex networks. This leads to a significant improvement in the performance of the synchronization criteria, i.e., less conservative synchronization results can be obtained. Meanwhile, the case of fast time-varying delay can also be handled by the proposed method. Furthermore, based on the derived criteria, a robust synchronization criterion is obtained for the system with uncertainties both in coefficient and coupling matrix terms. Since an expression based on linear matrix inequality is used, the proposed criteria can be easily checked in practice. Finally, numerical examples are provided to show the effectiveness of the proposed method.
Melatonin regulates defense responses in plants under environmental stress. This study aimed to explore the impact of exogenous melatonin on the phenotype and physiology of 'BM1' pumpkin seedlings ...subjected to waterlogging stress. Waterlogging stress was induced following foliar spraying of melatonin at various concentrations (CK, 0, 10, 100, 200, and 300 μmol·L-1). The growth parameters, malondialdehyde (MDA) content, antioxidant enzyme activity, osmoregulatory substance levels, and other physiological indicators were assessed to elucidate the physiological mechanisms underlying the role of exogenous melatonin in mitigating waterlogging stress in pumpkin seedlings. The results indicate that pumpkin seedlings exhibit waterlogging symptoms, such as leaf wilting, water loss, edge chlorosis, and fading, under waterlogging stress conditions. Various growth indicators of the seedlings, including plant height, stem diameter, root length, fresh and dry weight, and leaf chlorophyll content, were significantly reduced. Moreover, the MDA content in leaves and roots increased significantly, along with elevated activities of superoxide dismutase, catalase, peroxidase, and soluble protein contents. When different concentrations of melatonin were sprayed on the leaves post waterlogging stress treatment, pumpkin seedlings showed varying degrees of recovery, with the 100 μmol·L-1 treatment displaying the best growth status and plant morphological phenotypes. There were no significant differences compared to the control group. Seedling growth indicators, chlorophyll content, root activity, antioxidant enzyme activities, soluble protein content, and osmotic adjustment substance content all increased to varying degrees with increasing melatonin concentration, peaking at 100 μmol·L-1. Melatonin also reduced membrane damage caused by oxidative stress and alleviated osmotic imbalance. Exogenous melatonin enhanced the activities of antioxidant enzymes and systems involved in scavenging reactive oxygen species, with 100 μmol·L-1 as the optimal concentration. These findings underscore the crucial role of exogenous melatonin in alleviating waterlogging stress in pumpkins. The findings of this study offer a theoretical framework and technical assistance for cultivating waterlogging-resistant pumpkins in practical settings. Additionally, it establishes a theoretical groundwork for the molecular breeding of pumpkins with increased tolerance to waterlogging.Melatonin regulates defense responses in plants under environmental stress. This study aimed to explore the impact of exogenous melatonin on the phenotype and physiology of 'BM1' pumpkin seedlings subjected to waterlogging stress. Waterlogging stress was induced following foliar spraying of melatonin at various concentrations (CK, 0, 10, 100, 200, and 300 μmol·L-1). The growth parameters, malondialdehyde (MDA) content, antioxidant enzyme activity, osmoregulatory substance levels, and other physiological indicators were assessed to elucidate the physiological mechanisms underlying the role of exogenous melatonin in mitigating waterlogging stress in pumpkin seedlings. The results indicate that pumpkin seedlings exhibit waterlogging symptoms, such as leaf wilting, water loss, edge chlorosis, and fading, under waterlogging stress conditions. Various growth indicators of the seedlings, including plant height, stem diameter, root length, fresh and dry weight, and leaf chlorophyll content, were significantly reduced. Moreover, the MDA content in leaves and roots increased significantly, along with elevated activities of superoxide dismutase, catalase, peroxidase, and soluble protein contents. When different concentrations of melatonin were sprayed on the leaves post waterlogging stress treatment, pumpkin seedlings showed varying degrees of recovery, with the 100 μmol·L-1 treatment displaying the best growth status and plant morphological phenotypes. There were no significant differences compared to the control group. Seedling growth indicators, chlorophyll content, root activity, antioxidant enzyme activities, soluble protein content, and osmotic adjustment substance content all increased to varying degrees with increasing melatonin concentration, peaking at 100 μmol·L-1. Melatonin also reduced membrane damage caused by oxidative stress and alleviated osmotic imbalance. Exogenous melatonin enhanced the activities of antioxidant enzymes and systems involved in scavenging reactive oxygen species, with 100 μmol·L-1 as the optimal concentration. These findings underscore the crucial role of exogenous melatonin in alleviating waterlogging stress in pumpkins. The findings of this study offer a theoretical framework and technical assistance for cultivating waterlogging-resistant pumpkins in practical settings. Additionally, it establishes a theoretical groundwork for the molecular breeding of pumpkins with increased tolerance to waterlogging.
Background/Aims: Angiotensin converting enzyme 2 (ACE2) treatment suppresses the severity of acute lung injury (ALI). The effects of ACE2 in ALI have been shown to not only result from its ...antagonizing hydrolyzing angiotensin II (AngII), which is responsible for reduction in the vascular tension and pulmonary accumulation of inflammatory cells, but also result from a role of ACE2 in suppressing the ALI-induced apoptosis of pulmonary endothelial cells (PECs). Nevertheless, the underlying mechanisms of the role of ACE2 on PEC apoptosis are not completely understood. Methods: Here, we used a bleomycin-induced mouse model for ALI that has been published in our previous studies. We analyzed the mRNA and protein levels of an anti-apoptotic protein Bcl-2 in the ALI-mice that have been treated w/o ACE2. We analyzed miR-4262 levels in the mouse lung in these mice. Bcl-2-targeting miRNAs were predicted using bioinformatics algorithms and a luciferase reporter assay was applied to examine the effects of miR-4262 on the Bcl-2 protein translation upon their binding to 3'-UTR of Bcl-2 mRNA. Adeno-associated viruses carrying either miR-4262 mimics or antisense were injected into ALI-mice without ACE2, and their effects on the apoptosis in mouse lung cells were analyzed by Western blot. Results: ACE2 inhibited the ALI-induced apoptosis of pulmonary cells in vivo partially through upregulation of Bcl-2 protein, but not Bcl-2 mRNA. ACE2 appeared to significantly suppress the upregulation of miR-4262 in mouse lung after ALI. MiR-4262 was found to target 3'-UTR of Bcl-2 mRNA to inhibit its protein translation in PECs. In vivo administration of antisense of miR-4262 decreased apoptosis of pulmonary cells and severity of the ALI in mice. Conclusion: ACE2-induced suppression of miR-4262 partially contribute to the inhibition of the PEC apoptosis after ALI through Bcl-2. MiR-4262 may be a novel promising treatment target for ALI and ARDS.
Satellite precipitation products have been applied to many research fields due to their high spatial and temporal resolution. However, satellite inversion of precipitation is indirect, and different ...inversion algorithms limit the accuracy of the measurement results, which leads to great uncertainty. Therefore, it is of great significance to quantify and record the error characteristics of different satellite precipitation products for their better application in hydrology and other research fields. In this study, based on CN05.1, which is a set of site–based interpolation data, we evaluated the accuracies of the six satellite precipitation datasets (IMERG–E, IMERG–L, IMERG–F, GSMaP, CMORPH, and PERSIANN–CDR) at different temporal scales (daily, monthly, and yearly) in mainland China for the period from 2001 to 2015. The results were as follows: (1) In terms of mean precipitation, IMERG–F was superior to other data in all areas. IMERG products and PERANN–CDR performed better than other products at all scales and were more suitable for precipitation research in mainland China. Site correction can effectively improve the accuracy of product inversion, so IMERG–F was significantly better than IMERG–E and IMERG–L. (2) Except PERSIANN–CDR, all precipitation products underestimated precipitation in the range of 1–4 mm/day and had a high coincidence with CN05.1 in the range of 4–128 mm/day. (3) The performance of six types of satellite precipitation products in summer was better than that in winter. However, the error was larger in seasons with more precipitation. (4) In the Qinghai–Tibet Plateau, where there are few stations, the inversion of precipitation by satellite products is closer to the actual situation, which is noteworthy. These results help users understand the characteristics of these products and improve algorithms for future algorithm developers.
In this work, the first-principles calculation was performed to investigate the effect mechanism of Zn, Ni and Mn solute elements on the WC/Cu-based filler metal interfacial properties, and the ...CuZnNiMn filler metal was designed, the diffusion behavior of interface elements was verified by experiments. Firstly, Zn, Ni and Mn element doping WC/Cu interface models were established respectively. The effect natures of alloying elements on the interfacial properties were explored by adhesive strength and interfacial electronic structure. The results show that Zn element slightly aggregate into the Cu matrix interior after full relaxation, which has little effect on the interface structure, but it can lower the melting point and optimize the properties of Cu-based filler metals. Ni, Mn elements tend to segregate toward the interface and form strong covalent bonds and metallic bonds with W atoms, which can significantly improve the interfacial bonding strength of WC/Cu. The Energy Dispersive Spectroscopy (EDS) analysis of the WC/CuZnNiMn interface region proves that the diffusion effect of Zn in the interface is not obvious, while the Ni and Mn elements strongly diffuse into the WC particle, which has a positive effect on the metallurgical bonding of the brazed joint.
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