Changchun Observatory

We propose a method to invert surface wave dispersion data directly for 3-D variations of shear wave speed, that is, without the intermediate step of phase or group velocity maps, using frequency-dependent ray tracing and a wavelet-based sparsity-constrained tomographic inversion. A fast marching method is used to compute, at each period, surface wave traveltimes and ray paths between sources and receivers. This avoids the assumption of great-circle propagation that is used in most surface wave tomographic studies, but which is not appropriate in complex media. To simplify the problem we consider quasi-stratified media with smoothly varying seismic properties. We represent the 3-D shear wave speed model by means of 1-D profiles beneath grid points, which are determined from all dispersion data simultaneously using a wavelet-based sparsity-constrained tomographic method. The wavelet coefficients of the wave speed model are estimated with an iteratively reweighted least squares algorithm, and upon iteration the surface wave ray paths and the data sensitivity matrix are updated using the newly obtained wave speed model. To demonstrate its feasibility, we apply the method to determine the 3-D shallow crustal shear wave speed variations in the Taipei basin of Taiwan using short period interstation Rayleigh wave phase velocity dispersion measurements extracted from the ambient noise cross-correlation method. The results are consistent with previous studies and reveal strong shallow crustal heterogeneity that correlates with surface geology.

Preparation of branched polyethylenimine grafted electrospun polyacrylonitrile fiber membrane for effective adsorption and filtration of Cr(<sc>vi</sc>).

Abstract The Tibetan Plateau (TP) impacts local and remote atmospheric circulations, wherein it mechanically and thermally affects air masses or airflows. Moreover, the TP provides a key channel for substance transport between the troposphere and the stratosphere. This study reviews recent advances in research regarding land–atmosphere coupling processes over the TP. The TP experiences climate warming and wetting. Climate warming has caused glacier retreat, permafrost degradation, and a general increase in vegetation density, while climate wetting has led to a significant increase in the number of major lakes, primarily through increased precipitation. Local and regional climates are affected by interactions between the land and the atmosphere. Namely, the TP drives surface pollutants to the upper troposphere in an Asian summer monsoon (ASM) anticyclone circulation, before spreading to the lower stratosphere. Further, the thermal forcing of the TP plays an essential role in the ASM. TP forcing can modulate hemispheric‐scale atmospheric circulations across all seasons. The TP interacts with remote oceans through a forced atmospheric response and is substantially affected by the evolution of the Earth's climate via promoting Atlantic meridional overturning circulation and eliminating Pacific meridional overturning circulation. The extensive influence of the TP is facilitated by its coupling with the ASM in the summer; whereas its winter influence on climate mainly occurs through Rossby waves. The observed increasing trends of temperature and precipitation over the TP are projected to continue throughout the 21st century.

Abstract Silicate rock weathering maintains a stable and long‐term absorption of CO 2 . However, the magnitude, spatial pattern, and evolution characteristics of global silicate rock weathering carbon sink (SCS) remain unclear. To solve this problem, based on high‐precision hydrometeorological data (1996–2017) and CMIP5 data (2041–2060), using the Celine model, we calculated the global silicate rock weathering carbon sink flux (SCSF) magnitude and spatio‐temporal distribution for 1996–2017. We also predicted the SCSF under two future greenhouse gas emission scenarios (RCP 4.5 and RCP 8.5). Then, we produced a spatial data set (0.5 × 0.5) of global SCSF from 1996 to 2017 and found that the global average annual SCSF was 1.67 t/km 2 /yr, and the SCS was 127.11 Tg/yr. In particular, Brazil's silicate rock contribution accounts for nearly a quarter of the global SCS (24.41%). Although the GEM‐CO 2 model is now widely used, the SCSF, without considering the temperature, may be overestimated by 5.4%, and the maximum contribution of temperature to it can reach 240 kg/km 2 /yr. Moreover, the global SCS is now showing a downward trend, but the global emission of greenhouse gases in the future (2041–2060) will continue to increase the carbon sink capacity (23.8%) due to temperature changes. In summary, we have produced a set of high‐resolution spatiotemporal data of the past and the future. The above results fill up the large‐scale data gap of SCSF and provide a scientific basis for quantitatively assessing the impact of climate change on SCS.

Abstract We determined three‐dimensional P and S wave velocities and P wave azimuthal anisotropic tomography of the Northwest Pacific subduction zones by inverting 1,225,086 P wave and 335,117 S wave arrival times from 13,413 earthquakes. Our results show some differences between P and S wave images for the stagnant Pacific slab in the mantle transition zone (MTZ) beneath Northeast China. The stagnant slab looks thicker in the P wave image than that in the S wave image, which may reflects the effects of both hydration and lower temperature in the MTZ, though differences in the resolution of P and S wave tomography may also have some effects. The Changbai intraplate volcanism is caused by hot and wet upwelling in the big mantle wedge above the stagnant Pacific slab. Our P wave anisotropy tomography shows that the fast velocity direction (FVD) in the subducting Philippine Sea plate beneath the Ryukyu arc is NE‐SW (trench parallel), which is consistent with the spreading direction of the West Philippine Basin during its initial opening stage, suggesting that it may reflect the fossil anisotropy. A striking variation of the FVD with depth is revealed in the subducting Pacific slab beneath the Northeast Japan arc, which may be caused by slab dehydration that changed elastic properties of the slab with depth. The FVD in the mantle wedge beneath the Northeast Japan and Ryukyu arcs is trench normal, which reflects subduction‐induced convection. Beneath the Kuril and Izu‐Bonin arcs where oblique subduction occurs, the FVD in the mantle wedge is nearly normal to the moving direction of the downgoing Pacific plate, suggesting that the oblique subduction together with the complex slab morphology have disturbed the mantle flow.

Over 12 years of continuous monitoring of Changbaishan volcano in the border region of China and North Korea by means of volcanic seismicity, ground deformation, and volcanic gas geochemistry yields new evidence for magmatic unrest of the volcano between 2002 and 2006. In this so‐called “active period,” the frequency of volcanic earthquakes increased by about 2 orders of magnitude compared to that of the background “inactive periods.” The active period was also accompanied by ground inflation, high values of CO 2 , He, H 2 , and high ratios of N 2 /O 2 and 3 He/ 4 He in volcanic gases released from three hot springs near the caldera rim. The monitoring evidence implies pressurization of the magma chamber, possibly caused by incremental magma recharge. The ground deformation data from both GPS and precise leveling are modeled to suggest the corresponding deformation source is at 2–60 km depth beneath the volcano's summit, where earthquake swarms were detected in 2002 and 2003. Our findings suggest that the magma chamber beneath Changbaishan volcano has awakened and resumed activity after remaining dormant since AD 1903. There is an urgent need to keep close watch on this active and very hazardous volcano in northeast China.

Inflammation and autophagy occur during hepatic fibrosis development caused by various pathogens, and effectively curbing of autophage may delay the occurrence of hepatic fibrosis. The current study aimed to unravel the inhibitory effects of Ginsenoside Rg3 (G-Rg3) on inflammation-mediated hepatic autophagy to curb hepatic fibrosis caused by thioacetamide (TAA)-induced subacute and chronic hepatic injury. TAA is mainly metabolized in the liver to cause liver dysfunction. After intraperitoneal injection of TAA for 4 or 10 weeks (TAA-chronic mouse models), severe inflammatory infiltration and fibrosis occurred in the liver. Treatment with G-Rg3 alleviated hepatic pathological changes and reversed hepatic fibrosis in the TAA-chronic models with decreased deposition of collagen fibers, reduced expression of HSCs activation marker (α-SMA), and reduced secretion of profibrogenic factors (TGF-β1). G-Rg3 decreased expressions of autophagy-related proteins in mice of TAA-chronic models. Notably, G-Rg3 inhibited the survival of activated rat hepatic stellate cells (HSC-T6), but had no cytotoxicity on human hepatocytes (L02 cell lines). G-Rg3 dose-dependently inhibited autophagy in vitro with less expression of p62 and fewer LC3a transformation into LC3b in inflammatory inducer lipopolysaccharide (LPS)-induced rat HSC-T6 cells. Furthermore, G-Rg3 enhanced the phosphorylation of phosphatidylinositol 3-kinase (PI3K) and protein kinase B (Akt) in vivo and in vitro. Besides, mTOR inhibitor Rapamycin and PI3K inhibitors LY294002 were employed in LPS-treated HSC-T6 cell cultures to verify that Rg3 partially reversed the increase in autophagy in hepatic fibrosis in vitro. Taken together, G-Rg3 exerted anti-fibrosis effect through the inhibition of autophagy in TAA-treated mice and LPS-stimulated HSC-T6 cells. These data collectively unravel that G-Rg3 may serve a promising anti-hepatic fibrosis drug.

The Environmental Satellite (Envisat) mission was finished on April 8, 2012, and since that time, the attitude of the satellite has undergone significant changes. During the International Laser Ranging Service campaign, the Satellite Laser Ranging (SLR) stations have performed the range measurements to the satellite that allowed determination of the attitude and the spin period of Envisat during seven months of 2013. The spin axis of the satellite is stable within the radial coordinate system (RCS; fixed with the orbit) and is pointing in the direction opposite to the normal vector of the orbital plane in such a way that the spin axis makes an angle of 61.86° with the nadir vector and 90.69° with the along-track vector. The offset between the symmetry axis of the retroreflector panel and the spin axis of the satellite is 2.52 m and causes the meter-scale oscillations of the range measurements between the ground SLR system and the satellite during a pass. Envisat rotates in the counterclockwise (CCW) direction, with an inertial period of 134.74 s (September 25, 2013), and the spin period increases by 36.7 ms/day.

Computational deconvolution with single-cell RNA sequencing data as reference is pivotal to interpreting spatial transcriptomics data, but the current methods are limited to cell-type resolution. Here we present Redeconve, an algorithm to deconvolute spatial transcriptomics data at single-cell resolution, enabling interpretation of spatial transcriptomics data with thousands of nuanced cell states. We benchmark Redeconve with the state-of-the-art algorithms on diverse spatial transcriptomics platforms and datasets and demonstrate the superiority of Redeconve in terms of accuracy, resolution, robustness, and speed. Application to a human pancreatic cancer dataset reveals cancer-clone-specific T cell infiltration, and application to lymph node samples identifies differential cytotoxic T cells between IgA+ and IgG+ spots, providing novel insights into tumor immunology and the regulatory mechanisms underlying antibody class switch.

Understanding the spatial patterns of plant communities is important for sustainable wetland ecosystem management and biodiversity conservation. With the rapid development of unmanned aerial vehicle (UAV) technology, UAV-borne hyperspectral data with high spatial resolution have become ideal for accurate classification of wetland plant communities. In this article, four dominant plant communities (Phragmites australis, Typha orientalis, Suaeda glauca, and Scirpus triqueter) and two unvegetated cover types (water and bare land) in the Momoge Ramsar wetland site were classified. This was achieved using UAV hyperspectral images and three object- and pixel-based machine-learning classification algorithms [random forest (RF), convolutional neural network (CNN), and support vector machine (SVM)]. First, spectral derivative analysis, logarithmic analysis, and continuum removal analysis identified the wavelength at which the greatest difference in reflectance occurs. Second, dimensionality reduction of hyperspectral images was conducted using principal component analysis. Subsequently, an optimal feature combination for community mapping was formed based on data transformation (spectral features, vegetation indices, and principal components). Image objects were obtained by segmenting the optimum object feature subsets. Finally, distribution maps of communities were produced by using three machine-learning classification algorithms. Our results reveal that object-based image analysis outperforms pixel-based methods, with overall accuracies (OAs) of 80.29-87.75%; RF has the highest OA of 87.75% (Kappa = 0.864), followed consecutively by CNN (OA = 83.31%, Kappa = 0.829) and SVM (OA = 80.29%, Kappa = 0.813). Phragmites australis dominates the plant community (55.9%) at the study area, followed by Typha orientalis (16.2%), Suaeda glauca (16.2%), and Scirpus triqueter (4.6%). The results highlight the importance of spectral transformation features in red-edge regions. The mapping results will help establish basic information for subsequent studies involving habitat suitability assessment at this study site.

Abstract High‐quality soil moisture (SM) datasets are in great demand for climate, hydrology, and other fields, but detailed evaluation of SM products from various sources is scarce. Thus, using 670 SM stations worldwide, we evaluated and compared SM products from microwave remote sensing [Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR‐E) (C‐ and X‐bands) and European Space Agency's Climate Change Initiative (ESA CCI)], land surface model [Global Land Data Assimilation System (GLDAS)], and reanalysis data [ECMWF Re‐Analysis‐Interim (ERA‐Interim) and National Centers for Environmental Prediction (NCEP)] under different time scales and various climates and land covers. We find that: (a) ESA CCI and GLDAS have the closest values to the in situ SM on the annual scale, whereas others overestimate the SM; ERA‐Interim (averaged R = 0.58) and ESA CCI (averaged R = 0.54) correlate best with the in situ data, while GLDAS performs worst. (b) Overall, the deviations of each product vary in seasons. ESA CCI and ERA‐Interim products are closer to the in situ SM at seasonal scales, and AMSR‐E and NCEP perform worst in December–February and June–August, respectively. (c) Except for NCEP and ERA‐Interim, others can well reflect the intermonthly variation of the in situ SM. (d) Under various climates and land covers, AMSR‐E products are less effective in cold climates, whereas GLDAS and NCEP products perform poorly in arid or temperate and dry climates. Moreover, the Bias and R of each SM product differ obviously under different forest types, especially the AMSR‐E products. In summary, SM from ESA CCI is the best, followed by ERA‐Interim product, and precipitation is an important auxiliary data for selecting high‐quality SM stations and improving the accuracy of SM from GLDAS. These results can provide a reference for improving the accuracy of the above SM products.

Due to its small size, large specific surface area and hydrophobicity, microplastics, and the adsorbed contaminants may together cause potential negative effects on ecosystems and human beings. In this study, kinetics and size effects on adsorption of Cu(II), Cr(III), and Pb(II) onto PE, PP and PET microplastic particles were explored. Results indicated that the PE and PET microplastics have the higher adsorption capacity for Cu(II), Cr(III), and Pb(II) than that for PP microplastic. The adsorption capacity was affected by microplastic types and metal species. Among the three metals, Pb(II) had the largest adsorption amount on microplastic particles, especially on PET particles. Moreover, the adsorption capacities of microplastics increase with the decrease of particle size. The metal adsorption capacity of &amp;lt;0.9 mm microplastics is greater than that of 0.9–2 mm and 2–5 mm microplastics. The size effect on metal adsorption was largest for PE microplastic. More attention should be paid in case of the coexistence of heavy metals and tiny PE and PET microplastics in the environment.

In this paper, we propose and demonstrate an all-fiber passively Q-switched erbium doped fiber laser (EDFL) by using gold nanostars (GNSs) as a saturable absorber (SA) for the first time, to the best of our knowledge. In comparison with other gold nanomorphologies, GNSs have multiple localized surface plasmon resonances, which means that they can be used to construct wideband ultrafast pulse lasers. By inserting the GNS SA into an EDFL cavity pumped by a 980 nm laser diode, a stable passively Q-switched laser at 1564.5 nm was achieved for a threshold pump power of 40 mW. By gradually increasing the pump power from 40 to 120 mW, the pulse duration decreases from 12.8 to 5.3 μs and the repetition rate increases from 10 to 17 kHz. Our results indicate that the GNSs are a promising SA for constructing pulse lasers.

Deep learning (DL)-based fault diagnosis models have to collect the most comprehensive data of mechanical fault types to ensure reliability. In real scenarios, due to complex, variable operating conditions, machines often generate unexpected faults that lead to an increment of fault types, causing the diagnosis model to be invalid. Therefore, the data of new fault types are needed to retrain the model. However, DL models suffer from catastrophic forgetting when incrementally learning new classes. To solve the problem of the diagnosis of increasing fault types, a lifelong learning method for fault diagnosis (LLMFD) is proposed in this paper under the lifelong learning paradigm. The key of LLMFD is a proposed dual-branch aggregation networks (DBANets) framework that is combined with reserved exemplars to learn the new fault types without forgetting the old ones. In DBANets, each residual block layer has a dynamic block and a steady block to solve the stability&#x2013;plasticity dilemma in lifelong learning. The aggregation weights are adopted to balance stability and plasticity. LLMFD is applied to a diagnosis case of incremental fault types. Results verify that LLMFD is superior to other lifelong learning methods and has satisfactory robustness.

Abstract Studied in this article are the properties of the electromagnetic (EM) fields generated by an earthquake due to the motional induction effect, which arises from the motion of the conducting crust across the Earth's magnetic field. By solving the governing equations that couple the elastodynamic equations with Maxwell equations, we derive the seismoelectromagnetic wavefields excited by a single‐point force and a double‐couple source in a full space. Two types of EM disturbances can be generated, i.e., the coseismic EM field accompanying the seismic wave and the independently propagating EM wave which arrives much earlier than the seismic wave. Simulation of an M w 6.1 earthquake shows that at a receiving location where the seismic acceleration is on the order of 0.1 m/s 2 , the coseismic electric and magnetic fields are on the orders of 1 μV/m and 0.1 nT, respectively, agreeing with the EM data observed in 2008 M w 6.1 Qingchuan earthquake, China, and indicating that the motional induction effect is effective enough to generate observable EM signal. We also simulated the EM signals observed by Haines et al. ( ) which were called the Lorentz fields and cannot be explained by the electrokinetic effect. The result shows that the EM wave generated by a horizontal force can explain the data well, suggesting that the motional induction effect is responsible for the Lorentz fields. The motional induction effect is compared with the electrokinetic effect, showing the overall conclusion that the former dominates the mechanoelectric conversion under low‐frequency and high‐conductivity conditions while the latter dominates under high‐frequency and low‐conductivity conditions.

In order to solve the problems that local minimum, path planning in obstacles, and optimizing global obstacle avoidance path, the paper proposed a new obstacle avoidance method. In this method, used the grid method to describe the information of obstacles environment, utilized the evolutionary artificial potential field method to optimize obstacle avoidance path. The simulation results show that the proposed method is feasible and effective.

Abstract On 16 September 2015, an M w 8.3 earthquake struck middle Chile due to the subduction of the Nazca plate beneath the South America plate. This earthquake is the consequence of 72 years of strain accumulation in the region since the 1943 M 8.3 event. In this study, we apply the compressive sensing method (CS) to invert for the spatiotemporal distribution of the coseismic radiation at different frequencies of this event. The results show clear frequency‐dependent feature of earthquake rupture with low‐frequency (LF) radiation located in the updip region while high‐frequency (HF) radiation concentrated in the downdip region of the megathrust. We also compare the CS results with three coseismic slip models as well as the stress drop distributions inferred from these slip models. The comparison confirms our understanding of coseismic radiation that energy sources are mostly located in the margin of large coseismic slip regions. Furthermore, we find that the LF radiation sources are mainly within the stress‐decreasing (releasing) regions while the HF radiation sources are mainly located in the stress‐increasing (loading) regions due to rupturing of relatively large asperities nearby (stress decreasing and releasing). These results help to better understand the physics of the rupture process during megathrust earthquakes. Moreover, our results do not show radiation sources south of the epicenter, suggesting that the subducting Juan Fernandez Ridge probably stopped the rupture of this earthquake toward the south.

In this work, we carry out numerical simulations of the seismo-electromagnetic fields associated with a fault in a porous medium by considering the electrokinetic effect. In addition to porous materials, the adopted layered models comprise solid materials in which the electrokinetic effect is inoperative. First, sensitivity study is performed for the evanescent and direct radiation electromagnetic (EM) waves generated by a double couple point source embedded in a porous half-space below a solid half-space. Results suggest that both the evanescent and direct radiation EM waves are sensitive to some medium properties, for example porosity, salinity, fluid viscosity, and conductivity of solid layer. Then, adopting an eight-layer half-space model, we simulate the seismic and EM wavefields generated by the rupture process of a finite fault. It is shown that the electrokinetic effect is able to generate observable corupture EM signals, but the observability depends on some factors such as the epicentral distance, properties of the medium where the fault is located, and local activity levels of EM noise. Time synchronization coseismic EM signals are recorded when the receiver is close to the ground water level but located in a solid medium. In addition to the post-seismic electric field, our results also show the post-seismic magnetic field which has not been identified in previous simulation studies on the electrokinetic effect. The generation of the post-seismic magnetic field probably requires a sufficiently strong medium heterogeneity or fluid-pressure gradient.

Abstract Orthopyroxene (opx) is an important mineral in petrologic models for the upper mantle. Its elastic properties are fundamental for understanding the chemical composition and geodynamics of the upper mantle. Here we calculate the elastic properties of orthoenstatite (MgSiO 3 ), the Mg end‐member orthopyroxene under upper mantle pressure and temperature conditions using first principle calculations with local density approximation. Bulk and shear moduli increase nonlinearly with pressure at mantle temperatures, but the shear modulus and V S show very weak pressure dependence in comparison with V P . Compared to other major minerals in the upper mantle, orthoenstatite has the lowest compressional velocities ( V P ), shear velocities ( V S ), and V P / V S ratio down to the depth of approximately 300 km. The enrichment of opx in the upper mantle can cause the unusually low V P / V S observed in the mantle wedge.

Abstract At the core‐mantle boundary, most observed ultralow velocity zones (ULVZs) cluster along the edges of the large low shear velocity provinces (LLSVPs) and provide key information on the composition, dynamics, and evolution of the lower mantle. However, their detailed structure near slab‐like structures beneath the mid‐Pacific remains particularly challenging because of the lack of station coverage. While most studies of ULVZs concentrate on SKS‐complexity, here we report on the multipathing of ScS, which expands the sampling for ULVZs. We find the strongest multipathing along a ULVZ patch located just south of Hawaii and the far northeastern edge of the LLSVP, in a zone ~200 km in width and extending 600 km southward. The anomalous ScS travel times and distorted S diff waveforms further reveal patches interrupted by observed enhanced D″ indicative of slab‐debris influence on the complexity of the northeastern boundary of the mid‐Pacific LLSVP.