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Dicranopteris is the most representative pioneer species, dominant species and key species in degraded slope land in South China. Dicranopteris could quickly form dense synusia of a single and dominant species. In contrast to the traditional view that Dicranopteris hinders forest regeneration, we found that there are a few species that could settle down in Dicranopteris synusia. We proposed a hypothesis that Dicranopteris synusia could act as an ecological filter. In this study, we transplanted 12 target species seedlings under Dicranopteris synusia with 4 treatments to explore the ecological filtering effect of Dicranopteris synusia, and analyzed the mechanism with soil characteristics. The 4 treatments included the understory removal treatment (UR), the aboveground of Dicranopteris synusia were kept (AF), the root blanket of Dicranopteris synusia were kept (AR) and all of the Dicranopteris were kept (CK). The results showed that: 1) Compared with the red soil under Dicranopteris synusia of Eucalyptus plantation and bare ground, the contents of soil organic matter, total nitrogen, hydrolyzed nitrogen, available phosphorus, available potassium, and exchangeable base ions in the root blanket of Dicranopteris synusia were significantly higher. 2) The majority of the tree species and all of the herbaceous species could not survive with the root blanket of Dicranopteris synusia kept (AR and CK). The species that could survive with the root blanket of Dicranopteris synusia kept were Schima superba, Rhodomyrtus tomentosa, Ilex asprella and Melastoma candidum. The results indicated that Dicranopteris synusia could act as an ecological filter. The key lies in the role of root blanket of Dicranopteris synusia, and not in the improvement of soil nutrients. Theoretically, Dicranopteris synusia, especially the root blanket of Dicranopteris synusia, is closely related to the breakthrough of biological threshold for ecological restoration. In the future, it is necessary to further analyze the structure and function of the root blanket of Dicranopteris synusia. In terms of application, there are a large number of plantation types (such as Eucalyptus plantation) that Dicranopteris occupied as a single dominant understory species in South China. Therefore, we should pay more attention to the ecological filtering effect of Dicranopteris synusia in structural optimization and stand transformation. This study could provide a reference for the restoration and reconstruction of degraded slope land in South China.

In this paper, adaptive fuzzy fault-tolerant control (AFFTC) for the attitude control system of a hypersonic gliding vehicle (HGV) experiencing an actuator fault is proposed. Actuator faults of the HGV are considered with respect to its actual structure and actuator characteristics. The HGV's attitude system is firstly represented by a T–S fuzzy model, and then a normal T–S fuzzy controller is designed. A reinforcement learning (RL)-based policy iterative solution algorithm is proposed for the solving of the T-S fuzzy controller. Then, based on the normal T–S controller, a fuzzy FTC controller is proposed in which the control matrices can improve themselves according to the special fault. An integral reinforcement learning (IRL)-based solving algorithm is proposed to reduce the dependence of the design methods on the HGV model. Simulations on three different kinds of actuator faults show that the designed IRL-based FTC can ensure a reliable flight by the HGV. [ABSTRACT FROM AUTHOR]

Aims Elucidating the impacts of long-term spaceflight on cardiovascular health is urgently needed in face of the rapid development of human space exploration. Recent reports including the NASA Twins Study on vascular deconditioning and aging of astronauts in spaceflight are controversial. The aims of this study were to elucidate whether long-term microgravity promotes vascular aging and the underlying mechanisms. Methods and results Hindlimb unloading (HU) by tail suspension was used to simulate microgravity in rats and mice. The dynamic changes of carotid stiffness in rats during 8 weeks of HU were determined. Simulated microgravity led to carotid artery aging-like changes as evidenced by increased stiffness, thickness, fibrosis, and elevated senescence biomarkers in the HU rats. Specific deletion of the mechanotransducer Piezo1 in vascular smooth muscles significantly blunted these aging-like changes in mice. Mechanistically, mechanical stretch-induced activation of Piezo1 elevated microRNA-582-5p in vascular smooth muscle cells, with resultant enhanced synthetic cell phenotype and increased collagen deposition via PTEN/PI3K/Akt signalling. Importantly, inhibition of miRNA-582-5p alleviated carotid fibrosis and stiffness not only in HU rats but also in aged rats. Conclusions Long-term simulated microgravity induces carotid aging-like changes via the mechanotransducer Piezo1-initiated and miRNA-mediated mechanism. [ABSTRACT FROM AUTHOR]

Sea-ice mapping using Synthetic Aperture Radar (SAR) in the melt season poses challenges, primarily due to meltwater complicating the distinguishability of sea-ice types. In response to this issue, this study introduces a novel method for classifying sea ice during the Bohai Sea's melting period. The method categorizes sea ice into five types: open water (OW), gray ice (Gi), melting gray ice (GiW), gray–white Ice (Gw), and melting gray–white Ice (GwW). To achieve this classification, 51 polarimetric features are extracted from L-, S-, and C-band PolSAR data using various polarization decomposition methods. This study assesses the separability of these features among different combinations of sea-ice type by calculating the Euclidean distance (ED). The Support Vector Machine (SVM) classifier, when employed with single-frequency polarimetric feature sets, achieves the highest accuracy for OW and Gi in the C-band, GiW in the S-band, and Gw and GwW in the L-band. Remarkably, the C-band features exhibit the overall highest accuracy when compared to the L-band and S-band. Furthermore, employing a multi-dimensional polarimetric feature set significantly improves classification accuracy to 94.55%, representing a substantial enhancement of 9% to 22% compared to single-frequency classification. Benefiting from the performance advantages of Random Forest (RF) classifiers in handling large datasets, RF classifiers achieve the highest classification accuracy of 95.84%. The optimal multi-dimensional feature composition includes the following: L-band: SE, SEI, α ¯ , Span; S-band: SEI, SE, Span, PV-Freeman, λ1, λ2; C-band: SE, SEI, Span, λ3, PV-Freeman. The results of this study provide a reliable new method for future sea-ice monitoring during the melting season. [ABSTRACT FROM AUTHOR]

How to distinguish the relative role of climate change and human activities in vegetation dynamics has attracted increasing attention. However, most of the current studies concentrate on arid and semiarid regions, while the relative contributions of climate change and human activities to vegetation changes remain unclear in warm-humid regions. Based on the normalized difference vegetation index (NDVI) and climatic variables (temperature, precipitation, radiation) during 2001–2020, this study used the Theil–Sen median trend analysis, partial correlation analysis, and residual trend analysis to analyze the spatiotemporal pattern of vegetation trends, the response of vegetation to climate variations, and the climatic and anthropogenic contributions to vegetation dynamics in the warm and humid Guangdong Province of south China. Results showed that the NDVI in most areas exhibited an increasing trend. Changes in climatic variables displayed different spatial variations which, however, were not significant in most areas. Vegetation responded diversely to climate change with temperature as the most important climatic factor for vegetation improvement in most areas, while precipitation was the dominant climatic factor in the southern edge region and radiation was the dominant climatic factor in the central and western regions. Vegetation in most areas was influenced by both climate change and human activities, but the contribution rate of human activities was commonly much higher than climate change. The findings of this study are expected to enhance our understanding of the relative climatic and anthropogenic contributions to vegetation changes in warm-humid regions and provide a scientific basis for future ecological policies and ecosystem management in highly urbanized regions. [ABSTRACT FROM AUTHOR]