Search

Since 2016, the Argo (Array for Real-Time Geostrophic Oceanography) ocean salinity data has exhibited significant drift, directly affecting the accurate quantification of the global steric sea level (SSL) rates. To further investigate how salinity drift affects the estimation of SSL rates in different depths and regions, we divide the 0–2000 m into three layers (0–300 m, 300–1000 m and 1000–2000 m) and select five open oceans (the South and North Pacific, the South and North Atlantic, and the Indian Ocean) for discussion. By comparing the SSL rates between the periods of 2005–2015 and 2005–2019, we can evaluate the impact of salinity drift. Taking the estimated results from the IPRC (provided by the International Pacific Research Center at the University of Hawaii) and BOA (provided by the Second Institute of Oceanography, China) data as examples, we find that the effect of salinity drift is the largest at the depth of 1000–2000 m, about 29% for IPRC data and about 18% for BOA data. Moreover, the South Atlantic is susceptible to the effects of salinity drift, with an approximately 13% impact for IPRC data and 21% for BOA data.

Drought is one of the most significant limiting factors affecting plant growth and development on the Qinghai–Tibet Plateau (QTP). Mining the drought-tolerant genes of the endemic perennial grass of the QTP, Siberian wildrye (Elymus sibiricus), is of great significance to creating new drought-resistant varieties which can be used in the development of grassland livestock and restoring natural grassland projects in the QTP. To investigate the transcriptomic responsiveness of E. sibiricus to drought stress, PEG-induced short- and long-term drought stress was applied to two Siberian wildrye genotypes (drought-tolerant and drought-sensitive accessions), followed by third- and second-generation transcriptome sequencing analysis. A total of 40,708 isoforms were detected, of which 10,659 differentially expressed genes (DEGs) were common to both genotypes. There were 2107 and 2498 unique DEGs in the drought-tolerant and drought-sensitive genotypes, respectively. Additionally, 2798 and 1850 DEGs were identified in the drought-tolerant genotype only under short- and long-term conditions, respectively. DEGs numbering 1641 and 1330 were identified in the drought-sensitive genotype only under short- and long-term conditions, respectively. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed that all the DEGs responding to drought stress in E. sibiricus were mainly associated with the mitogen-activated protein kinase (MAKP) signaling pathway, plant hormone signal transduction, the linoleic acid metabolism pathway, the ribosome pathway, and plant circadian rhythms. In addition, Nitrate transporter 1/Peptide transporter family protein 3.1 (NPF3.1) and Auxin/Indole-3-Acetic Acid (Aux/IAA) family protein 31(IAA31) also played an important role in helping E. sibiricus resist drought. This study used transcriptomics to investigate how E. sibiricus responds to drought stress, and may provide genetic resources and references for research into the molecular mechanisms of drought resistance in native perennial grasses and for breeding drought-tolerant varieties.

This study applies Gravity Recovery and Climate Experiment (GRACE) data and the WaterGAP (Water Global Analysis and Prognosis) Global Hydrology Model (WGHM) to investigate the influence of the Bui reservoir operation on water storage variation within the Volta River Basin (VRB). Variation in groundwater storage anomalies (GWSA) was estimated by combining GRACE-derived terrestrial water storage anomalies (TWSA), radar altimetry records, imagery-derived reservoir (Lake Volta and Bui) surface water storage anomalies (SWSA), and Global Land Data Assimilation System (GLDAS)-simulated soil moisture storage anomalies (SMSA) from 2002 to 2016. Results showed that TWSA increased (1.30 ± 0.23 cm/year) and decreased (−0.82 ± 0.27 cm/year) during 2002–2011 and 2011–2016, respectively, within VRB, matching previous TWSA investigations in this area. It revealed that the multi-year averages of monthly GRACE-derived TWSA changes in 2011–2016 displayed an overall increasing trend, indicating storage increase in regional hydrology; while the Lake Volta water storage changes decreased. The GRACE-minus-WGHM residuals display an increasing trend in VRB water storage during the Bui reservoir impoundment during 2011–2016. The observed trend compares well with the estimated Bui reservoir SWSA, indicating that GRACE solutions can retrieve the true amplitude of large mass changes happening in a concentrated area, though Bui reservoir is much smaller than the resolution of GRACE global solutions. It also revealed that GWSA were almost stable from 2002 to 2006, before increasing and decreasing during 2006–2011 and 2012–2016 with rates of 2.67 ± 0.34 cm/year and −1.80 ± 0.32 cm/year, respectively. The observed trends in the GRACE-derived TWSA and GWSA changes are generally attributed to the hydro-meteorological conditions. This study shows that the effects of strong El-Niño Southern Oscillation events on the GWSA interannual variability within the VRB is short-term, with a lag of 6 months. This study specifically showed that the Bui reservoir operation significantly affects the TWSA changes and provides knowledge on groundwater storage changes within the VRB.

As a major contributor to global mean sea-level rise, the Greenland ice sheet (GrIS) and the patterns of its mass change have attracted wide attention. Based on Gravity Recovery and Climate Experiment (GRACE)/GRACE Follow-On (GRACE-FO) gravimetry data, we computed monthly non-cumulative mass change time series of the GrIS, which agree with those from the mass budget method confirming the reliability of GRACE-FO-derived mass change. Over the GrIS, mass was mainly gained in winter, followed by spring. It primarily lost mass in summer, with the percentage of summer mass loss versus the corresponding annual mass loss ranging from 61% to 96%. We report that spring mass loss has become more frequent since 2015, and autumn mass gain occurred more frequently after 2014. By separating mass gain from mass loss at the annual timescale, we find that both the mass gain and mass loss showed a slightly increasing trend during 2003–2020, which might be a response to the ongoing Arctic warming. Summer mass variations highly correlated with the summer North Atlantic Oscillation index are dominated by temperature-associated precipitation and meltwater runoff. This study suggests that long-term observations would be necessary to better understand patterns of the GrIS mass variations in future.

Catalytic membranes, as a combination of heterogeneous advanced oxidation and membrane technology reaction systems, have important application prospects in the treatment of dyes and other organics. In practical applications, it is still challenging to construct catalytic membranes with excellent removal efficiency and fouling mitigation. Herein, molybdenum disulfide-iron oxyhydroxide (MoS2-FeOOH) was fabricated using iron oxide and MoS2 nanoflakes, which were synthesized by the hydrothermal method. Furthermore, by changing the concentration of MoS2-FeOOH, the MoS2-FeOOH/polyethersulfone (PES) composite ultrafiltration membrane was obtained with improved hydrophilicity, permeability, and antifouling capacity. The pure water flux of the composite membrane reached 385.3 L/(m2·h), which was 1.7 times that of the blank PES membrane. Compared with the blank membrane, with the increase of MoS2-FeOOH content, the MoS2-FeOOH/PES composite membranes had better adsorption capacity and catalytic performance, and the membrane with 3.0% MoS2-FeOOH content (M4) could be achieved at a 60.2% methylene blue (MB) degradation rate. In addition, the membrane flux recovery ratio (FRR) of the composite membrane also increased from 25.6% of blank PES membrane (M0) to more than 70% after two cycles of bovine serum albumin (BSA) filtration and hydraulic cleaning. The membrane with 2.25% MoS2-FeOOH content (M3) had the best antifouling performance, with the largest FRR and the smallest irreversible ratio (Rir). Catalytic self-cleaning of the composite membrane M3 recovered 95% of the initial flux with 0.1 mol/L H2O2 cleaning. The MoS2-FeOOH/PES composite membranes with the functions of excellent rejection and antifouling capacity have a good prospect in the treatment of printing and dyeing wastewater composed of soluble dyes.

Replacing estimates of C20 from the Gravity Recovery and Climate Experiment (GRACE) monthly gravity field solutions by those from satellite laser ranging (SLR) data and including degree one terms has become a standard procedure for proper science applications in the satellite gravimetry community. Here, we assess the impact of degree one terms, SLR-based C20 and C30 estimates on GRACE-derived polar ice sheet mass variations. We report that degree one terms recommended for GRACE Release 06 (RL06) data have an impact of 2.5 times more than those for GRACE RL05 data on the mass trend estimates over the Greenland and the Antarctic ice sheets. The latest recommended C20 solutions in GRACE Technical Note 14 (TN14) affect the mass trend estimates of ice sheets in absolute value by more than 50%, as compared to those in TN11 and TN07. The SLR-based C30 replacement has some impact on the Antarctic ice sheet mass variations, mainly depending on the length of the study period. This study emphasizes that reliable solutions of low degree spherical harmonics are crucial for accurately deriving ice sheet mass balance from satellite gravimetry.

To investigate aerosol radiative effects, the Sun–Sky Radiometer Observation Network (SONET) has performed long-term observations of columnar atmospheric aerosol properties at 20 distributed stations around China. The aerosol direct radiative forcing (RF) and efficiency (RFE, the rate at which the atmosphere is forced per unit of aerosol optical depth) were estimated using radiative transfer model simulations based on the ground-based observations dating back to 2009. Results of multi-year monthly average RF illustrated that: the dust-dominant aerosol population at arid and semi-arid sites exerted moderate cooling effects (−8.0~−31.2 W/m2) at the top and bottom of atmosphere (TOA and BOA); RF at continental background site was very weak (−0.8~−2.9 W/m2); fine-mode dominant aerosols at urban and suburban sites exerted moderate cooling effects (−9.3~−24.1 W/m2) at TOA but more significant cooling effects (−19.4~−50.6 W/m2) at BOA; RF at coastal sites was comparable with values of urban sites (−5.5~−19.5 W/m2 at TOA, and −15.6~−44.6 W/m2 at BOA), owing to combined influences by marine and urban–industrial aerosols. Differences between RFE at TOA and BOA indicated that coarse-mode dominant aerosols at arid, semi-arid, and continental background sites were less efficient to warm the atmosphere; but fine-mode dominant aerosols at urban, suburban, and coastal sites were shown to be more efficient to heat the atmosphere.

Aerosol optical depth (AOD) derived from satellite remote sensing is widely used to estimate surface PM2.5 (dry mass concentration of particles with an in situ aerodynamic diameter smaller than 2.5 µm) concentrations. In this research, a two-stage spatio-temporal statistical model for estimating daily surface PM2.5 concentrations in the Guanzhong Basin of China is proposed, using 6 km × 6 km AOD data available from the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument as the main variable and meteorological factors, land-cover, and population data as auxiliary variables. The model is validated using a cross-validation method. The linear mixed effects (LME) model used in the first stage could be improved by using a geographically weighted regression (GWR) model or the generalized additive model (GAM) in the second stage, and the predictive capability of the GWR model is better than that of GAM. The two-stage spatio-temporal statistical model of LME and GWR successfully captures the temporal and spatial variations. The coefficient of determination (R2), the bias and the root-mean-squared prediction errors (RMSEs) of the model fitting to the two-stage spatio-temporal models of LME and GWR were 0.802, −0.378 µg/m3, and 12.746 µg/m3, respectively, and the model cross-validation results were 0.703, 1.451 µg/m3, and 15.731 µg/m3, respectively. The model prediction maps show that the topography has a strong influence on the spatial distribution of the PM2.5 concentrations in the Guanzhong Basin, and PM2.5 concentrations vary with the seasons. This method can provide reliable PM2.5 predictions to reduce the bias of exposure assessment in air pollution and health research.

Satellite gravimetry data acquired by the Gravity Recovery and Climate Experiment (GRACE) allows to derive the temporal evolution in ice mass for both the Antarctic Ice Sheet (AIS) and the Greenland Ice Sheet (GIS). Various algorithms have been used in a wide range of studies to generate Gravimetric Mass Balance (GMB) products. Results from different studies may be affected by substantial differences in the processing, including the applied algorithm, the utilised background models and the time period under consideration. This study gives a detailed description of an assessment of the performance of GMB algorithms using actual GRACE monthly solutions for a prescribed period as well as synthetic data sets. The inter-comparison exercise was conducted in the scope of the European Space Agency’s Climate Change Initiative (CCI) project for the AIS and GIS, and was, for the first time, open to everyone. GMB products generated by different groups could be evaluated and directly compared against each other. For the period from 2003-02 to 2013-12, estimated linear trends in ice mass vary between −99 Gt/yr and −108 Gt/yr for the AIS and between −252 Gt/yr and −274 Gt/yr for the GIS, respectively. The spread between the solutions is larger if smaller drainage basins or gridded GMB products are considered. Finally, findings from the exercise formed the basis to select the algorithms used for the GMB product generation within the AIS and GIS CCI project.

The Danjiangkou Reservoir (DJKR) is the freshwater source for the Middle Route of the South-to-North Water Diversion Project in China, and its water level and storage changes are important for water resource management. To maximize the potential capacity of the Gravity Recovery and Climate Experiment (GRACE) mission, an improved Lagrange multiplier method (ILMM) is first proposed to detect terrestrial water storage anomalies (TWSA) in the small-scale basin (DJKR). Moreover, for the first time, water diversion fingerprints are proposed to analyze the spatiotemporal pattern of the TWSA in the DJKR. The results indicate that the increased water level and storage signals due to the DJKR impoundment in 2014 can be effectively detected by using the ILMM, and they agree well with the results from altimetry and in situ data. Additionally, the water diversion fingerprints due to the DJKR impoundment are inferred, and describe the progression of spatiotemporal variability in water storage. The results show that water storage decreased in the upper Hanjiang River and increased in the DJKR as well as to the east of it during the period 2013−2015. Our research provides a scientific decision-making basis for monitoring the water resources of the DJKR and managing the South-to-North Water Diversion Project.

A thorough understanding of aerosol optical properties and their spatio-temporal variability are required to accurately evaluate aerosol effects in the climate system. In this study, a multi-year study of aerosol optical and microphysical properties was firstly performed in Xi’an based on three years of sun photometer remote sensing measurements from 2012 to 2015. The multi-year average of aerosol optical depth (AOD) at 440 nm was about 0.88 ± 0.24 (mean ± SD), while the averaged Ångström Exponent (AE) between 440 and 870 nm was 1.02 ± 0.15. The mean value of single scattering albedo (SSA) was around 0.89 ± 0.03. Aerosol optical depth and AE showed different seasonal variation patterns. Aerosol optical depth was slightly higher in winter (0.99 ± 0.36) than in other seasons (~0.85 ± 0.20), while AE showed its minimum in spring (0.85 ± 0.05) due to the impact of dust episodes. The seasonal variations of volume particle size distribution, spectral refractive index, SSA, and asymmetry factor were also analyzed to characterize aerosols over this region. Based on the aerosol products derived from sun photometer measurements, the classification of aerosol types was also conducted using two different methods in this region. Results show that the dominant aerosol types are absorbers in all seasons, especially in winter, demonstrating the strong absorptivity of aerosols in Xi’an.

The mitochondrial calcium uniporters (MCUs) are a family of calcium unidirectional transporters important for cytoplasmic Ca2+ signals. Though the MCU proteins in several plant species have been investigated, genome-wide analysis of MCUs in alfalfa is lacking. Here, via genome-wide analysis, a total of 5, 20, and 6 MCU genes were identified in three different alfalfa cultivars, namely Medicago truncatula Jemalong A17, Medicago sativa XinJiangDaYe, and M. sativa Zhongmu No. 1, respectively. They were further phylogenetically classified into three subfamilies. Most MCU genes have only one intron, and gene duplication events of MCU genes were observed within each alfalfa accession and between different accessions. All alfalfa MCU proteins contained a highly conserved MCU domain and 10 conserved motifs, featuring two transmembrane domains and a DI/VME motif. According to the tissue expression data of M. sativa Zhongmu No. 1, MsMCU6.2 was the most abundant transcript with the highest expression in the leaf, and MsMCU5 and MsMCU1.2 showed higher expression levels in the stem than other tissues. We analyzed the expression profiles of five MCU genes (MsMCU1.1/1.2/5/6.1/6.2) under salt, drought, and cold stresses via qRT-PCR assays. All five MCU genes were induced by drought stress, except MsMCU5, whose expression was up-regulated by salt stress, while cold stress slightly altered MsMCU expression. Nine potential interacting proteins and three miRNAs targeting MtMCUs were predicted. These results provide detailed knowledge of alfalfa MCU genes and suggest their potential functions in abiotic stress response.

In this paper, we investigate the relationships among point transitivity, topological transitivity, Li–Yorke chaos, and the existence of irregular vectors for a linear semiflow {Tt}t∈Δ indexed with a complex sector. We reveal the equivalence between topological transitivity and point transitivity for a linear semiflow {Tt}t∈Δ, especially in case the range of some operator Tt,t∈Δ is not dense. We also prove that Li–Yorke chaos is equivalent to the existence of a semi-irregular vector and that point transitivity is stronger than the existence of an irregular vector for any linear semiflow Ttt∈Δ. At last, unlike the conclusion for traditional linear dynamical systems, we show that there exists a Li–Yorke chaotic C0-semigroup Ttt∈Δ without irregular vectors. The results and proof methods presented in this paper demonstrate the differences in the dynamical behavior between linear semiflows {Tt}t∈Δ and traditional linear systems with the acting semigroup S=Z+ and S=R+.

Photodetectors play a critical role in space lidars designed for scientific investigations from orbit around planetary bodies. The detectors must be highly sensitive due to the long range of measurements and tight constraints on the size, weight, and power of the instrument. The detectors must also be space radiation tolerant over multi-year mission lifetimes with no significant performance degradation. Early space lidars used diode-pumped Nd:YAG lasers with a single beam for range and atmospheric backscattering measurements at 1064 nm or its frequency harmonics. The photodetectors used were single-element photomultiplier tubes and infrared performance-enhanced silicon avalanche photodiodes. Space lidars have advanced to multiple beams for surface topographic mapping and active infrared spectroscopic measurements of atmospheric species and surface composition, which demand increased performance and new capabilities for lidar detectors. Higher sensitivity detectors are required so that multi-beam and multi-wavelength measurements can be performed without increasing the laser and instrument power. Pixelated photodetectors are needed so that a single detector assembly can be used for simultaneous multi-channel measurements. Photon-counting photodetectors are needed for active spectroscopy measurements from short-wave infrared to mid-wave infrared. HgCdTe avalanche photodiode arrays have emerged recently as a promising technology to fill these needs. This paper gives a review of the photodetectors used in past and present lidars and the development and outlook of HgCdTe APD arrays for future space lidars.

2-naphthylamine (NAP) was classified as a group I carcinogen associated with bladder cancer. The daily exposure is mostly from cigarette and E-cigarette smoke. NAP can lead to testicular atrophy and interstitial tissue hyperplasia; however, the outcomes of NAP treatment on spermatogenesis and the associated mechanisms have not been reported. The study aimed to investigate the effect of NAP on spermatogenesis and sperm physiologic functions after being persistently exposed to NAP at 5, 20, and 40 mg/kg for 35 days. We found that sperm motility, progressive motility, sperm average path velocity, and straight-line velocity declined remarkably in the NAP (40 mg/kg) treated group, and the sperm deformation rate rose upon NAP administration. The testis immunity- and lipid metabolism-associated processes were enriched from RNA-sequence profiling. Plvap, Ccr7, Foxn1, Trim29, Sirpb1c, Cfd, and Lpar4 involved in testis immunity and Pnliprp1 that inhibit triglyceride and cholesterol absorption were confirmed to rise dramatically in the NAP-exposed group. The increased total cholesterol and CD68 levels were observed in the testis from the NAP-exposed group. Gpx5, serving as an antioxidant in sperm plasma, and Semg1, which contributes to sperm progressive motility, were both down-regulated. We concluded that the short-term exposure to NAP caused reproductive toxicity, primarily due to the inflammatory abnormality in the testis.

Trust plays a crucial role in effectively responding to public health emergencies. Drawing on COVID-19 survey data conducted in Hubei, China, during August 2020 with a sample size of 5494, this study investigated the influence of individuals’ socioeconomic status on trust in acquaintances, strangers and institutions, and how this relationship is moderated by epidemic prevention, policy perception and family structure. The findings showed that individuals with higher socioeconomic status tend to have higher levels of trust. Those with higher income but being married demonstrate higher trust. When perceiving epidemic prevention policies as stringent, those with higher income display increased trust in acquaintances and institutions; similarly, those with lower education levels exhibit heightened trust in acquaintances and strangers. Individuals working in social organizations express higher trust in strangers; however, their trust is compromised under stringent epidemic prevention policies due to potentially heavier work burdens.

The low obliquity of the Moon leads to challenging solar illumination conditions at the poles, especially for passive reflectance measurements aimed at determining the presence and extent of surface volatiles. A nascent alternate method is to use active laser illumination sources in either a multispectral or hyperspectral design. With a laser spectral source, however, the achievable reflectance precision may be limited by speckle noise resulting from the interference effects of a coherent beam interacting with a rough surface. Here, we have experimentally tested the use of laser linewidth broadening to reduce speckle noise and, thus, increase reflectance precision. We performed a series of speckle imaging tests with near-infrared laser sources of varying coherence, compared them to both theory and speckle pattern simulations, and measured the reflectance precision using calibrated targets. By increasing the laser linewidth, we observed a reduction in speckle contrast and the corresponding increase in reflectance precision, which was 80% of the theoretical improvement. Finally, we discuss methods of laser linewidth broadening and spectral resolution requirements for planetary laser reflectance spectrometers.

Plant height and leaf area index (LAI) are crucial growth indicators that reflect the growth status of tomatoes in greenhouses, enabling accurate determinations to effectively estimate crop transpiration and formulate irrigation strategies for reducing agricultural water waste. There is a need for the increased application of related models to simulate tomato growth indices in the traditional greenhouse production in China. This study proposes a nondestructive, real-time monitoring and simulation device for measuring tomato plant height and leaf area index. The weight of aboveground tomatoes was obtained by suspending tomato plants on dynamometers, while the total weight of stem and leaf organs was determined using a distribution coefficient simulation model. The R2 value between the measurements from the electronic scale and those from the aboveground fresh weight device for tomatoes was 0.937, with an RMSE value of 0.05 kg. The monitoring device did not affect the average tomato growth during operation. The device will not affect the growth of tomatoes during monitoring. A multiple linear regression was used to compare the measured and simulated values of the plant height and leaf area index of various types of greenhouse tomatoes cultivated in different greenhouse types. The average R2 value for simulating plant height was 0.817 with an RMSE of 10.81 cm. The average R2 value for the leaf area index was 0.854, with an RMSE of 0.55 m2·m−2. The simulated values for plant height and leaf area index closely matched the measured values, indicating that the model has high accuracy and applicability in traditional Chinese greenhouses (solar greenhouses and insulated plastic greenhouses). However, further optimization is required for commercially produced, continuous plastic greenhouses equipped with greenhouse environmental control equipment.

Transit-oriented development (TOD) has become a dominant form of spatial planning and land use in large cities internationally. As the intersections of urban space and rail transportation, metro station areas play a key public service function in the lives of city residents. Based on the “5D” index and Node-Place theory in the metro station area, current research on the built environment in metro station areas focuses on improving the economic and transportation efficiency while neglecting public perception of the construction of station space. Sentiments, as an important part of the individual’s perception, are closely related to the built environment. Therefore, this study takes 187 metro stations within the fifth ring road of Beijing, China, as an example and extracts public sentiment information from social media data using a wide range of natural language processing techniques to quantitatively analyze the distribution of the public’s sentiment characteristics (including intensity, polarity, and category) in the metro station area and deeply explores the spatial correlation with the distribution of the objective built environment elements. The study shows that influenced by the spatial design of the metro station, density, land use functions, etc., the sentiment intensity of the station area within the Fifth Ring Road of Beijing is “strong in the east and weak in the west, strong in the north and weak in the south”, and the sentiment polarity has the characteristic of gradually negative from inside to outside in a circular pattern. Synthesizing the sentiment perception in the metro station area, our study further divided the Beijing metro station area into four major categories and eight specific subtypes.

Chemical kinetic studies of the β-scission reaction class of hydroperoxyl alkyl hydroperoxyl radicals (•P(OOH)2) from normal-alkyl cyclohexanes are carried out systematically through high-level ab initio calculations. Geometry optimizations and frequency calculations for all species involved in the reactions are performed at the B3LYP/CBSB7 level of theory. Electronic single-point energy calculations are calculated at the CBS-QB3 level of theory. Rate constants for the reactions of β-scission, in the temperature range of 500–1500 K and the pressure range of 0.01–100 atm, are calculated using transition state theory (TST) and Rice-Ramsberger-Kassel-Marcus/Master-Equation (RRKM/ME) theory taking asymmetric Eckart tunneling corrections and the one-dimensional hindered rotor approximation into consideration. The rate rules are obtained by averaging the rate constants of the representative reactions of this class. These rate rules can greatly assist in constructing more accurate low-temperature combustion mechanisms for normal-alkyl cyclohexanes.

By optimizing the reconfigurable intelligent surface (RIS) reflection coefficients, the channel capacity of legitimate users can be increased, thereby enhancing the anti-jamming performance of communication systems. However, existing studies on RIS-assisted anti-jamming assume that there is no coupling between the RIS reflection coefficients and the incident angle of electromagnetic (EM) waves, which is quite unreasonable. Therefore, we consider the effect of the incident angle of EM waves on the reflection coefficients of the RIS and propose a communication anti-jamming scheme assisted by an RIS with angular response. Specifically, a problem is formulated to optimize the RIS reflection coefficients so that the legitimate signal is amplified, but the jamming signal is attenuated, thus enhancing the legitimate channel capacity. However, the coupling of the EM incident angle and the RIS reflection coefficients causes the problem to be non-convex. To tackle this problem, we equivalently transform the RIS reflection coefficients optimization problem into a quadratically constrained quadratic programming (QCQP) problem using the complex Taylor expansion and the multidimensional complex quadratic transform (MCQT) and solve it utilizing the alternating direction method of the multipliers (ADMM) algorithm. The simulation results reveal that, compared to other schemes supported by RIS without angular response, the proposed scheme is able to achieve a significant improvement in the anti-jamming performance.

Thick red clay in northern China contains rich information about the uplifting of the Qinghai–Tibet Plateau, the drying process of Asian inland, the East Asian monsoon changes, and global cooling since 22 Ma. In comparison, the red clay widely distributed in southern China is generally much younger (

In order to comprehensively and accurately evaluate the adsorption effect of Eichhornia crassipes planting on algae in water, this study used 131 cloudless Sentinel-2 images to monitor the scale and growth dynamics of Eichhornia crassipes planting in Caohai and its surrounding waters. Based on the single and multi-peak histogram characteristics of the NDWI image in the study area, the empirical threshold and the optimized histogram slope adaptive threshold (OHSAT) segmentation methods were respectively used and manual inspection was added to accurately segment the water bodies and Eichhornia crassipes. The results of the analysis of Eichhornia crassipes area, growth status (NDVI), water body algae density (NDVI), and their spatial–temporal co-variation and trends show that the Eichhornia crassipes has a significant enrichment effect on algae, showing a significant decreasing trend of water bloom centered on it. The size and growth status of Eichhornia crassipes are inversely proportional to the water body NDVI, and reasonable harvesting plans based on these findings are expected to achieve optimized pollution control effects.

In this paper, a slot microring with an asymmetric grating structure is proposed. Through the coupling between the grating and the slot microring, a high free spectral range or EIT-like effects with a high quality factor can be achieved in the same device. The grating is designed as an asymmetric structure to realize the modulation of the optical signal and the control of the resonance peak by changing the grid number, and the effect of different grating periods on the output spectrum is explored. The results show that changing the grating on slot sidewalls can increase or decrease the number of resonant peaks. By selecting a specific period of the gratings on both sides of the slot, the distance between adjacent resonance peaks can be increased to achieve modulation of the free spectral range. In this paper, depending on the grating period, we obtain a quality factor of 5016 and an FSR of 137 nm, or a quality factor of 10,730 and an FSR of 92 nm. The refractive index sensing simulation is carried out for one of the periods, which can achieve a sensitivity of 370 nm/RIU. Therefore, the proposed new structure has certain advantages in different sensing applications.

The CRISPR-Cas system is a bacterial and archaea adaptive immune system and is a newly recognized mechanism for controlling antibiotic resistance gene transfer. Acinetobacter baumannii (A. baumannii) is an important organism responsible for a variety of nosocomial infections. A. baumannii infections have become problematic worldwide because of the resistance of A. baumannii to multiple antibiotics. Thus, it is clinically significant to explore the relationship between the CRISPR-Cas system and drug resistance in A. baumannii. This study aimed to analyze the genomic characteristics of the A. baumannii strain AB3 containing the type I-Fb CRISPR-Cas system, which was isolated from a tertiary care hospital in China, and to investigate the relationship between the CRISPR-Cas system and antibiotic resistance in this strain. The whole-genome sequencing (WGS) of the AB43 strain was performed using Illumina and PacBio sequencing. The complete genome of AB43 consisted of a 3,854,806 bp chromosome and a 104,309 bp plasmid. The specific characteristics of the CRISPR-Cas system in AB43 are described as follows: (1) The strain AB43 carries a complete type I-Fb CRISPR-Cas system; (2) Homology analysis confirmed that the cas genes in AB43 share high sequence similarity with the same subtype cas genes; (3) A total of 28 of 105 A. baumannii AB43 CRISPR spacers matched genes in the bacteriophage genome database and the plasmid database, implying that the CRISPR-Cas system in AB43 provides immunity against invasive bacteriophage and plasmids; (4) None of the CRISPR spacers in A. baumannii AB43 were matched with antimicrobial resistance genes in the NCBI database. In addition, we analyzed the presence of antibiotic resistance genes and insertion sequences in the AB43 strain and found that the number of antibiotic resistance genes was not lower than in the “no CRISPR-Cas system” strain. This study supports the idea that the CRISPR-Cas system may inhibit drug-resistance gene expression via endogenous gene regulation, except to the published mechanism that the CRISPR-Cas system efficiently limits the acquisition of antibiotic resistance genes that make bacteria sensitive to antibiotics.

Physical-layer key generation technology requires information reconciliation to correct channel estimation errors between two legitimate users. However, sending the reconciliation signals over the public channel increases the communication overhead and the risk of information leakage. Aiming at the problem, integrated secure communication schemes using non-reconciled keys have attracted extensive attention. These schemes exploit channel coding to correct both inconsistent keys and transmission error bits. Meanwhile, more redundant code bits must be added to correct errors, which results in a lower secure transmission rate. To address the problem, we analyze the merit of channel correlation between non-reconciled key generation and secure transmission. Inspired by this, we propose a non-reconciled physical-layer keys-assisted secure communication scheme based on channel correlation. First of all, the signal frame is designed to make use of channel correlation between non-reconciled key generation and secure transmission. Based on the channel correlation, non-reconciled keys are then generated from the wireless channel to encrypt transmitted data. Moreover, an adaptive coding algorithm based on the equivalent channel is presented to encode the data bits before encryption, to guarantee reliable transmission. Finally, theoretical analysis and simulations demonstrate the significant performance of the proposed scheme in terms of low bit error ratio and high secure transmission rate.

Pavement defect detection is critical for pavement maintenance and management. Meanwhile, the accurate and timely detection of pavement defects in complex backgrounds is a huge challenge for maintenance work. Therefore, this paper used a mask region-based convolutional neural network (Mask R-CNN) and transfer learning to detect pavement defects in complex backgrounds. Twelve hundred pavement images were collected, and a dataset containing corresponding instance labels of the defects was established. Based on this dataset, the performance of the Mask R-CNN was compared with faster region-based convolutional neural networks (Faster R-CNNs) under the transfer of six well-known backbone networks. The results confirmed that the classification accuracy of the two algorithms (Mask R-CNN and Faster R-CNN) was consistent and reached 100%; however, the average precision (AP) of the Mask R-CNN was higher than that of Faster R-CNNs. Meanwhile, the testing time of the models using a feature pyramid network (FPN) was lower than that of other models, which reached 0.21 s per frame (SPF). On this basis, the segmentation performance of the Mask R-CNN was further analyzed at three learning rates (LRs). The Mask R-CNN performed best with ResNet101 plus FPN as its backbone structure, and its AP reached 92.1%. The error rate of defect quantification was between 4% and 16%. It has an ideal detection effect on multi-object and multi-class defects on pavement surfaces, and the quantitative results of the defects can provide a reference for pavement maintenance personnel.

In this paper, we propose an improved physical layer key generation scheme that can maximize the secret key capacity by deploying intelligent reflecting surface (IRS) near the legitimate user aiming at improving its signal-to-noise ratio (SNR). We consider the scenario of multiple input single output (MISO) against multiple relevant eavesdroppers. We elaborately design and optimize the reflection coefficient matrix of IRS elements that can improve the legitimate user’s SNR through IRS passive beamforming and deteriorate the channel quality of eavesdroppers at the same time. We first derive the lower bound expression of the achievable key capacity, then solve the optimization problem based on semi-definite relaxation (SDR) and the convex–concave procedure (CCP) to maximize the secret key capacity. Simulation results show that our proposed scheme can significantly improve the secret key capacity and reduce hardware costs compared with other benchmark schemes.

Co-prime linear arrays (CLAs) provide an additional degree of freedom (DOF) with a limited number of physical sensors, and thus help to improve the resolution of direction of arrival (DOA) estimation algorithms. However, the DOF of traditional CLA is restrained by the structure of the array, which cannot be adjusted after deployment. In this paper, we propose a DOA estimation algorithm for reconfigurable intelligent surface co-prime linear array (RIS CLA) based on the multiple signal classification approach. Specifically, an RIS CLA is first constructed on the ground of RIS antenna, by turning on/off specific elements at different times. Then, the covariance matrix of the received signal is vectorized, so as to construct a virtual difference array, whose aperture is considerably expanded. Finally, a spectral peak search on the noise subspace of the received signal of the difference array is conducted to obtain the DOA estimation result. Simulations verify the improvement of the proposed algorithm in terms of DOF and resolution. To be specific, the DOF provided by RIS CLA outnumbers that of CLA by more than 30%, and the resolution of the proposed DOA estimation algorithm is effectively improved, with its accuracy increased up to 70% under the low signal-noise-ratio (SNR) scenario, compared with existing algorithms.

Tuning the high properties of segregated conductive polymer materials (CPCs) by incorporating nanoscale carbon fillers has drawn increasing attention in the industry and academy fields, although weak interfacial interaction of matrix-filler is a daunting challenge for high-loading CPCs. Herein, we present a facile and efficient strategy for preparing the segregated conducting ultra-high molecular weight polyethylene (UHMWPE)-based composites with acceptable mechanical properties. The interfacial interactions, mechanical properties, electrical properties and electromagnetic interference (EMI) shielding effectiveness (SE) of the UHMWPE/conducting carbon black (CCB) composites were investigated. The morphological and Raman mapping results showed that UHMWPE/high specific surface area CCB (h-CCB) composites demonstrate an obviously interfacial transition layer and strongly interfacial adhesion, as compared to UHMWPE/low specific surface area CCB (l-CCB) composites. Consequently, the high-loading UHMWPE/h-CCB composite (beyond 10 wt% CCB dosage) exhibits higher strength and elongation at break than the UHMWPE/l-CCB composite. Moreover, due to the formation of a densely stacked h-CCB network under the enhanced filler-matrix interfacial interactions, UHMWPE/h-CCB composite possesses a higher EMI SE than those of UHMWPE/l-CCB composites. The electrical conductivity and EMI SE value of the UHMWPE/h-CCB composite increase sharply with the increasing content of h-CCB. The EMI SE of UHMWPE/h-CCB composite with 10 wt% h-CCB is 22.3 dB at X-band, as four times that of the UHMWPE/l-CCB composite with same l-CCB dosage (5.6 dB). This work will help to manufacture a low-cost and high-performance EMI shielding material for modern electronic systems.

Space missions to study small solar system bodies, such as asteroids and comet cores, are enhanced by lidar that can provide global mapping and serve as navigation sensors for landing and surface sampling. A small swath-mapping lidar using a fiber laser modulated by pseudo-noise (PN) codes is well-suited to small space missions and can provide contiguous measurements of surface topography with

This paper presents a novel approach to substantially improve the detection accuracy of structural damage via a one-dimensional convolutional neural network (1-D CNN) and a decision-level fusion strategy. As structural damage usually induces changes in the dynamic responses of a structure, a CNN can effectively extract structural damage information from the vibration signals and classify them into the corresponding damage categories. However, it is difficult to build a large-scale sensor system in practical engineering; the collected vibration signals are usually non-synchronous and contain incomplete structure information, resulting in some evident errors in the decision stage of the CNN. In this study, the acceleration signals of multiple acquisition points were obtained, and the signals of each acquisition point were used to train a 1-D CNN, and their performances were evaluated by using the corresponding testing samples. Subsequently, the prediction results of all CNNs were fused (decision-level fusion) to obtain the integrated detection results. This method was validated using both numerical and experimental models and compared with a control experiment (data-level fusion) in which all the acceleration signals were used to train a CNN. The results confirmed that: by fusing the prediction results of multiple CNN models, the detection accuracy was significantly improved; for the numerical and experimental models, the detection accuracy was 10% and 16–30%, respectively, higher than that of the control experiment. It was demonstrated that: training a CNN using the acceleration signals of each acquisition point and making its own decision (the CNN output) and then fusing these decisions could effectively improve the accuracy of damage detection of the CNN.

We report the development of a new type of space lidar specifically designed for missions to small planetary bodies for both topographic mapping and support of sample collection or landing. The instrument is designed to have a wide dynamic range with several operation modes for different mission phases. The laser transmitter consists of a fiber laser that is intensity modulated with a return-to-zero pseudo-noise (RZPN) code. The receiver detects the coded pulse-train by correlating the detected signal with the RZPN kernel. Unlike regular pseudo noise (PN) lidars, the RZPN kernel is set to zero outside laser firing windows, which removes most of the background noise over the receiver integration time. This technique enables the use of low peak-power but high pulse-rate lasers, such as fiber lasers, for long-distance ranging without aliasing. The laser power and the internal gain of the detector can both be adjusted to give a wide measurement dynamic range. The laser modulation code pattern can also be reconfigured in orbit to optimize measurements to different measurement environments. The receiver uses a multi-pixel linear mode photon-counting HgCdTe avalanche photodiode (APD) array with near quantum limited sensitivity at near to mid infrared wavelengths where many fiber lasers and diode lasers operate. The instrument is modular and versatile and can be built mostly with components developed by the optical communication industry.

Repetitive operations have been extensively used in the inverter compressor refrigeration industry. The approximately periodic disturbance caused by repetitive operations must be compensated to realize stable and high-efficiency operation. In this paper, a periodic disturbance observer (PDOB) is proposed to tackle the speed fluctuation of an inverter compressor in the low-frequency range. Periodic disturbance, consisting of a fundamental wave and corresponding harmonics, can thus be estimated and compensated; in addition, sensitivity and complementary sensitivity can reach a compromise through the use of a certain parameter. Aiming at a different operation environment, an adaptive notch filter based on the Steiglitz–McBride method is employed to estimate the fundamental frequency of periodic disturbance. Finally, the feasibility of our approach is verified by MATLAB simulation, and experiments are implemented to illustrate that speed fluctuation can be more effectively attenuated by the proposed method in comparison with general DOB.

Phytochemical investigation of the n-BuOH extract of the rhizomes of Anemone rivularis var. flore-minore led to the isolation of five new oleanane-type triterpenoid saponins 1–5, together with five known saponins 6–10. Their structures were determined by the extensive use of 1D and 2D NMR experiments, along with ESIMS analyses and acid hydrolysis. The aglycone of 4 and 5 was determined as 21α-hydroxyoleanolic acid, which was reported in this genus for the first time. The cytotoxicity of these compounds was evaluated against four human cancer cell line, including HL-60 (promyelocytic leukemia), HepG2 (hepatocellular carcinoma), A549 (lung carcinoma) and HeLa (cervical carcinoma). The monodesmosidic saponins 6–8 exhibited cytotoxic activity toward all tested cancer cell lines, with IC50 values in the 7.25–22.38 μM range.

To reduce the dependence on oil and environmental pollution, the development of electric vehicles has been accelerated in many countries. The implementation of EVs, especially battery electric vehicles, is considered a solution to the energy crisis and environmental issues. This paper provides a comprehensive review of the technical development of EVs and emerging technologies for their future application. Key technologies regarding batteries, charging technology, electric motors and control, and charging infrastructure of EVs are summarized. This paper also highlights the technical challenges and emerging technologies for the improvement of efficiency, reliability, and safety of EVs in the coming stages as another contribution.

Temporal networks can describe multiple types of complex systems with temporal information in the real world. As an effective method for analyzing such network, temporal graph pattern (TGP) counting has received extensive attention and has been applied in diverse domains. In this paper, we study the problem of counting the TGP in the temporal network. Then, an exact algorithm is proposed based on the time first search (TFS) algorithm. This algorithm can reduce the intermediate results generated in the graph isomorphism and has high computational efficiency. To further improve the algorithm performance, we design an estimation algorithm by applying the edge sampling strategy to the exact algorithm. Finally, we evaluate the performances of the two algorithms by counting both the symmetric and asymmetric TGP. Extensive experiments on real datasets demonstrated that the exact algorithm is faster than the existing algorithm and the estimation algorithm can greatly reduce the running time while guaranteeing the accuracy.

Efficient and instant detection of biological threat-agent anthrax is highly desired in the fields of medical care and anti-terrorism. Herein, a new ratiometric fluorescence (FL) nanoprobe was elaborately tailored for the determination of 2,6-dipicolinic acid (DPA), a biomarker of anthrax spores, by grafting terbium ions (Tb3+) to the surface of carbon dots (CDs). CDs with blue FL were fabricated by a simple and green method using schizochytrium as precursor and served as an FL reference and a supporting substrate for coordination with Tb3+. On account of the absorbance energy transfer emission effect (AETE), green emission peaks of Tb3+ in CDs-Tb nanoprobe appeared at 545 nm upon the addition of DPA. Under optimal conditions, good linearity between the ratio FL intensity of F545/F445 and the concentrations of DPA was observed within the experimental concentration range of 0.5−6 μM with the detection limit of 35.9 nM, which is superior to several literature studies and significantly lower than the infectious dosage of the Bacillus anthracis spores. Moreover, the CDs-Tb nanoprobe could sensitively detect DPA in the lake water sample. This work offers an efficient self-calibrating and background-free method for the determination of DPA.

Open-source software has become a powerful engine for the development of the software industry. Its production mode, which is based on large-scale group collaboration, allows for the rapid and continuous evolution of open-source software on demand. As an important branch of open-source software, open-source operating systems are commonly used in modern service industries such as finance, logistics, education, medical care, e-commerce and tourism, etc. The reliability of these systems is increasingly valued. However, a self-organizing and loosely coupled development approach complicates the structural analysis of open-source operating system software. Traditional methods focus on analysis at the local level. There is a lack of research on the relationship between internal attributes and external overall characteristics. Consequently, conventional methods are difficult to adapt to complex software systems, especially the structural analysis of open-source operating system software. It is therefore of great significance to capture the holistic structure and behavior of the software system. Complex network theory, which is adequate for this task, can make up for the deficiency of traditional software structure evaluation methods that focus only on local structure. In this paper, we propose a package network model, which is a directed graph structure, to describe the dependency of open-source operating system software packages. Based on the Ubuntu Kylin Linux Operating system, we construct a software package dependency network of each distributed version and analyze the structural evolution through the dimensions of scale, density, connectivity, cohesion, and heterogeneity of each network.