•The time series reconstruction algorithm is applied to RSEI for the first time.•Corrected the correlation between RSEI and ecological components.•Alleviate the instability of RSEI time series.
...Remote Sensing Ecological Index (RSEI) is one of the most widely used ecological quality assessment indicators. Due to the noise caused by adverse atmoshperic conditions and other factors, the RSEI calculated from the original image usually has the phenomena of lack of information and unstable image quality. Therefore, based on Google Earth Engine (GEE) cloud platform, this study adopts three common data reconstruction algorithms firstly, namely: Savitory-Golay filter (SG), harmonic analysis of time series (HANTS), Whittaker Smoother (WS), which are used to reconstruct the original MODIS time series data in the Yangtze River Basin (YRB) from 2000 to 2020, in order to optimize the calculation process of RSEI. At the same time, three indicators (correlation coefficient (R), standard deviation (STD), root mean square error (RMSE)) are used for the accuracy evaluation. The results show that data reconstruction can fill gaps in RSEI, the reconstruction performance of WS and SG for four parameters is better than HANTS, and the four SG reconstructed sequences have the strongest correlation with the original sequences (R between 0.8 ∼ 1), while the WS reconstruction sequence has the lowest error value (both STD and RMSE are less than 1), both of them can correct the pixel value, which is conducive to maintaining the stability of RSEI in the temporal dimension; the RSEI produced by HANTS has the best accuracy, that is, R, STD, RMSE are respectively 0.898, 0.130, 0.104. As shown by the research, it is necessary to de-noise each parameter before synthesizing RSEI. This study can provide a theoretical basis for applying time-frequency algorithms to optimize the ecological monitoring performance of RSEI.
This article examines the positioning effect of integrated navigation after adding an LEO constellation signal source and a 5G ranging signal source in the context of China's new infrastructure ...construction. The tightly coupled Kalman federal filters are used as the algorithm framework. Each signal source required for integrated navigation is simulated in this article. At the same time, by limiting the range of the azimuth angle and visible height angle, different experimental scenes are simulated to verify the contribution of the new signal source to the traditional satellite navigation, and the positioning results are analyzed. Finally, the article compares the distribution of different federal filtering information factors and reveals the method of assigning information factors when combining navigation with sensors with different precision. The experimental results show that the addition of LEO constellation and 5G ranging signals improves the positioning accuracy of the original INS/GNSS by an order of magnitude and ensures a high degree of positioning continuity. Moreover, the experiment shows that the federated filtering algorithm can adapt to the combined navigation mode in different scenarios by combining different precision sensors for navigation positioning.
Mechanical fault diagnosis of high-voltage circuit breakers (HVCBs) based on vibration signal analysis is one of the most significant issues in improving the reliability and reducing the outage cost ...for power systems. The limitation of training samples and types of machine faults in HVCBs causes the existing mechanical fault diagnostic methods to recognize new types of machine faults easily without training samples as either a normal condition or a wrong fault type. A new mechanical fault diagnosis method for HVCBs based on variational mode decomposition (VMD) and multi-layer classifier (MLC) is proposed to improve the accuracy of fault diagnosis. First, HVCB vibration signals during operation are measured using an acceleration sensor. Second, a VMD algorithm is used to decompose the vibration signals into several intrinsic mode functions (IMFs). The IMF matrix is divided into submatrices to compute the local singular values (LSV). The maximum singular values of each submatrix are selected as the feature vectors for fault diagnosis. Finally, a MLC composed of two one-class support vector machines (OCSVMs) and a support vector machine (SVM) is constructed to identify the fault type. Two layers of independent OCSVM are adopted to distinguish normal or fault conditions with known or unknown fault types, respectively. On this basis, SVM recognizes the specific fault type. Real diagnostic experiments are conducted with a real SF₆ HVCB with normal and fault states. Three different faults (i.e., jam fault of the iron core, looseness of the base screw, and poor lubrication of the connecting lever) are simulated in a field experiment on a real HVCB to test the feasibility of the proposed method. Results show that the classification accuracy of the new method is superior to other traditional methods.
Amino-acid-derived phthalazine catalysts have been designed and synthesized for enantioselective halolactonization of prochiral dienoic acids. The scope of the reaction is evidenced by 17 examples of ...spiro α-exo-methylene-halolactones with up to 99.8% enantiomeric excess. The resulting enantio-enriched spiro halolactone products are found to exhibit potent antitumor effects. In addition, both antipodes of products with equally excellent enantioselevity could be obtained since a pair of enantiomeric catalysts is guaranteed.
Perpendicularly magnetized structures that are switchable using a spin current under field-free conditions can potentially be applied in spin–orbit torque magnetic random-access memory (SOT-MRAM). ...Several structures have been developed; however, new structures with a simple stack structure and MRAM compatibility are urgently needed. Herein, a typical structure in a perpendicular spin-transfer torque MRAM, the Pt/Co multilayer and its synthetic antiferromagnetic counterpart with perpendicular magnetic anisotropy, was observed to possess an intrinsic interlayer chiral interaction between neighboring magnetic layers, namely, the interlayer Dzyaloshinskii–Moriya interaction (DMI) effect. Furthermore, using a current parallel to the eigenvector of the interlayer DMI, we switched the perpendicular magnetization of both structures without a magnetic field, owing to the additional symmetry breaking introduced by the interlayer DMI. This SOT switching scheme realized in the Pt/Co multilayer and its synthetic antiferromagnet structure may open a new avenue toward practical perpendicular SOT-MRAM and other SOT devices.
To explore the potential of using the mineral alteration information extracted by remote sensing technology to indirectly estimate the heavy metal content of salinized soil, 23 sampling points were ...uniformly set up in the town of Gudao in the Yellow River Delta as the research area in 2022. The concentrations of seven heavy metals, Cr, Cu, Pb, Zn, As, Mn and Ni, at the sampling points were determined in laboratory tests. Spectral derivative indices, topographic factors, and mineral alteration information (iron staining, hydroxyl, and carbonate ions) were extracted and screened as modeling factors using Sentinel 2 imagery. An inverse model of heavy metal content was constructed using the random forest algorithm, and the model accuracy was evaluated using the cross-validation method. The results of the study show that: (1) Hydroxyl and carbonate ion alteration can be effectively used for the inversion of soil As and Ni content in this study area. Iron-stained alteration can be used as a modeling factor in the inversion of Cr, Cu, Pb, Zn, and Mn concentrations. (2) The inclusion of alteration information improves the accuracy of heavy metal content inversion. The Cu concentration was verified to be the best predictor, with an RMSE of 3.309, MAPE of 11.072%, and R
of 0.904, followed by As, Ni, and Zn; the predictive value of Mn, Cr and Pb was average. (3) Based on the results of concentration inversion, the high concentration areas of As, Ni, and Mn are primarily distributed on both sides of the river and around lakes and ponds. The high-concentration areas of Zn were mainly distributed in the farmland areas on both sides of the river. Areas with high concentrations of Cu were mainly distributed in the eastern oil extraction area, both sides of the rivers, and around lakes.
Background and Purpose
Neuronal regeneration from endogenous precursors is an attractive strategy for the treatment of ischaemic stroke. However, most stroke‐generated newborn neurons die over time. ...Therefore, a drug that is both neuroprotective and pro‐neurogenic may be beneficial after stroke. Here, we assessed the neurogenic and oligodendrogenic effects of tetramethylpyrazine nitrone (TBN), a neuroprotective drug candidate for stroke, in a rat model of ischaemic stroke.
Experimental Approach
We used Sprague Dawley rats with middle cerebral artery occlusion (MCAO). TBN was administered by tail vein injection beginning at 3 h post ischaemia. Therapeutic effect of TBN was evaluated by neurological behaviour and cerebral infarction. Promotion of neurogenesis and oligodendrogenesis was determined by double immunofluorescent staining and Western blotting analyses. Primary cultures of cortical neurons were used to assess the effect of TBN on neuronal differentiation in vitro.
Key Results
TBN reduced cerebral infarction, preserved and/or restored neurological function and promoted neurogenesis and oligodendrogenesis in rats after MCAO. In addition, TBN stimulated neuronal differentiation on primary culture of cortical neurons in vitro. Pro‐neurogenic effects of TBN were attributed to its activation of the AKT/cAMP responsive element‐binding protein through increasing brain‐derived neurotrophic factor (BDNF) expression, as shown by the abolition of the effects of TBN by a specific inhibitor of BDNF receptor ANA‐12 and by the PI3K inhibitor LY294002.
Conclusion and Implications
As TBN can simultaneously provide neuroprotection and pro‐neurogenic effects, it may be a promising treatment for both acute phase neuroprotection and long‐term functional recovery after ischaemic stroke.
Myocardial ischemia is a primary cause of sudden death worldwide. Numerous active ingredients of traditional Chinese medicines including danshensu (DSS) and tetramethylpyrazine (TMP) have been widely ...used for the treatment of myocardial ischemia. To enhance their therapeutic efficacy and improve their drugability, in this work, we designed new DSS and TMP conjugates. Their water solubility and protective effects were studied in vitro and in experimental animal models. The new compounds demonstrated higher activities than the positive control agents acetylated danshensu and tetramethylpyrazine conjugate (ADTM) and salvianolic acid B (SAB) in preventing cells from oxidative insult. Among the new compounds, 14, bearing two glycine moieties, was more water soluble. In addition, compound 14 was much more potent in preventing cells from oxidative injury, at least 10- and 20-fold as potent as ADTM and SAB, respectively. The protective effects of compound 14 may be attributed to its anti-radical activity and anti-apoptotic activity. These results suggest that compound 14 is a promising candidate for the treatment of myocardial ischemia.
Parkinson’s disease (PD) is the second most common neurodegenerative disease. Although the etiology of PD is not completely understood, it is well-documented that oxidative stress and Ca2+-mediated ...cellular damage play important roles in the progression of PD. 2-(1,1-Dimethylethyl)oxidoimino-methyl-3,5,6-trimethylpyrazine (TBN), a novel nitrone derivative of tetramethylpyrazine, has shown significant therapeutic effects in stroke models due to its multiple functions, including calcium overload blockade and free radical-scavenging. In this study, we investigated the neuroprotective and neurorescue effects of TBN on various in vitro and in vivo models of PD and explored its possible mechanisms of action. The results show that TBN exerted significant neuroprotection on 1-methyl-4-phenylpyridinium (MPP+)-induced damage in SH-SY5Y cells and primary dopaminergic neurons, as well as on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced dopaminergic neuron loss in zebrafish (TBN and MPTP were added simultaneously into the fish embryo medium and the treatment period was 48 h). In the MPTP-induced mouse and 6-hydroxydopamine (6-OHDA)-induced rat PD models, TBN administrated orally twice daily for 14 d (3 d post-MPTP lesion in mice and 7 d post-6-OHDA lesion in rats) exhibited remarkable neurorescue effects to increase the number of dopaminergic neurons. In addition, TBN improved apomorphine-induced rotational behavior in the 6-OHDA-lesioned PD rats. TBN suppressed the MPP+-induced intracellular reactive oxygen species (ROS) in SH-SY5Y cells, increased the superoxide dismutase (SOD) activity and glutathione (GSH) concentration in the substantial nigra of MPTP-treated mice. These data indicate that TBN protects and rescues dopaminergic neurons from MPP+ and MPTP/6-OHDA-induced damage by reducing ROS and increasing cellular antioxidative defense capability.
Polypharmacology-based strategies using drug combinations with different mechanisms of action are gaining increasing attention as a novel methodology to discover potentially innovative medicines for ...neurodegenerative disorders. We used this approach to examine the combined neuroprotective effects of two polyphenols, protocatechuic acid (PCA) and chrysin, identified from the fruits of Alpinia oxyphylla. Our results demonstrated synergistic neuroprotective effects, with chrysin enhancing the protective effects of PCA, resulting in greater cell viability and decreased lactate dehydrogenase release from 6-hydroxydopamine-treated PC12 cells. Their combination also significantly attenuated chemically induced dopaminergic neuron loss in both zebrafish and mice. We examined the molecular mechanisms underlying these collective cytoprotective effects through proteomic analysis of treated PC12 cells, resulting in the identification of 12 regulated proteins. Two were further characterized, leading to the determination that pretreatment with PCA and chrysin resulted in (i) increased nuclear factor-erythroid 2-related factor 2 protein expression and transcriptional activity; (ii) modulation of cellular redox status with the upregulated expression of hallmark antioxidant enzymes, including heme oxygenase-1, superoxide dismutase, and catalase; and (iii) decreased levels of malondialdehyde, a known lipid peroxidation product. Treatment with PCA and chrysin also inhibited activation of nuclear factor-κB and expression of inducible nitric oxide synthase. Our findings suggest that natural products, when used in combination, can be effective potential therapeutic agents for treating diseases such as Parkinson disease. A therapy involving both PCA and chrysin exhibits its enhanced neuroprotective effects through a combination of cellular mechanisms: antioxidant cytoprotection and anti-inflammation.
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•PCA and chrysin, extracted from Alpinia oxyphylla, efficiently treat in vivo and in vitro models of Parkinson disease.•The molecular mechanism for neuroprotection by PCA+chrysin in vitro involves modulation of the NRF2 and NF-κB pathways.•These results support the discovery and development of novel multiple-target therapeutics, especially natural medicines.
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