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A high-resolution helicopter cable obstacle avoidance LIDAR is designed by the laser parallel scanning method, combined with the 3×2 rectangular detector array, which greatly reduces the conventional laser radar in the detection of the cable blind area. By simulating the actual detection state of helicopter through the UAV hanging-off test, the cable at 150m is clearly detected at the data refresh rate of 2Hz. Through the range detection test, it is verified that the detection distance of the system for φ20 cable is more than 283m.

Once one of the most severe soil loss regions worldwide, the Chinese Loess Plateau has experienced large-scale land use changes and vegetation restoration in the past few decades. Understanding how land use change affects soil erosion is critical in the region's ecological construction and land management. In this study, the Beiluo River Basin covering 26,905 km2 in the hinterland of the Loess Plateau was selected to investigate vegetation restoration and its impacts on soil loss rates over the last 50 years. Results show that land use in the basin has changed considerably, mainly reflected in the upper reaches. From 1970–2020, cropland in the upper reaches decreased by 54%, directly leading to a 9.1-fold increase in forested land. Landsat-NDVI shows vegetation coverage increased from 21.1% to 69.9% over time. Vegetation coverage changed from 48.1% to 78.7% for the entire basin. The Chinese Soil Loss Equation (CSLE) was used and confirmed to be satisfactory with a high coefficient of determination (R2, 0.89) and a strong Nash–Sutcliffe efficiency coefficient (0.72), although an underestimation exists. With the change in land use, the specific soil loss simulated in the upper reaches maintained a high rate of around 8,000 t·km−2·yr−1 from the 1970s to the 1990s, dramatically dropping to 3,058 t·km−2·yr−1 in the 2000s, then attenuated to 1,321 t·km−2·yr−1 in the 2020s. For the entire basin, soil loss rates dropped from 4,090 to 1,848 and 890 t·km−2·yr−1 from the 1970s to the 2000s and 2020s, respectively. Attribution analysis showed that the dominant factor in the change in soil loss rates in the 1980s and 1990s relative to the 1970s was the change in rainfall erosivity for the entire watershed. However, with vegetation coverage increasing to 59.0% in the 2000s, vegetation restoration rapidly converted to the dominant factor contributing 78.3% to soil loss decrease in that period. With expanding vegetation cover, its contribution grew to 84.9% in the 2020s. The shift is evident in each reach of the basin except the terrain-plain area with the majority of farmland. The findings are helpful for sustainable land use planning and socio-economic development on the Loess Plateau and in similar areas.

Assessing ecological restoration effects on hydrological regimes is important for watershed management, especially under semi-arid conditions. The long-term trends of streamflow components were analyzed for three less forested watersheds (LFWs), and for two largely forested watersheds (FWs) within the Beiluo River Basin on the Chinese Loess Plateau. Three LFWs were undergoing major vegetation restoration, in which the vegetation coverage changed from 16–23% in 1970 to 57–80% coverage in 2019. While as contrast, the two FWs has vegetation coverage from 65–68% in 1970 to 88–92% in 2019. Daily flow data for each watershed and year were normalized by rainfall to eliminate effects of non-stationary rainfall. Mean annual streamflow totals for the ~60-year study period were 25.1–34.1 and 21.6–48.1 mm y_1 for the LFWs and FWs, respectively. Average contributions of baseflow to total streamflow were 32–44% for the LFWs and 58–61% for the FWs. Mann-Kendall tests showed significant decreasing trends for annual streamflow and stormflow (0.23–0.54% y_1) from the LFWs throughout. Mean streamflow from the LFWs between 2000 and 2019 decreased by 58% compared to the pre-2000 period, while the average contribution of stormflow decreased from 66% to 35% (2010s). However, winter baseflow increased with time since start of restoration. Conversely, streamflow (components) for the FWs showed only slight fluctuations in decadal, annual and seasonal trends. Both total streamflow and stormflow exhibited strong power relationships with vegetation coverage, illustrating a tendency towards stable flow regimes for vegetation coverage >60–70%. Large-scale vegetation restoration has fundamentally changed amounts and temporal distribution of streamflow (components) on the Loess Plateau mainly by regulating stormflow. After 20 years of restoration, the trend and proportion of streamflow components from the LFWs approximated those of the FWs. Since soil erosion is driven by a certain of amount and intensity of runoff, the above results imply that soil erosion and sediment transportation would reach a stability with vegetation restoration to a certain coverage in watersheds. But it is necessary to investigate the difference among regions. These results underpin the planning of sustainable management of natural resources and socio-economic development during long term ecological restoration on the Loess Plateau.Keywords: Trends of long-term hydrological elements; Surface flow and baseflow; Vegetation restoration; Loess Plateau

Soil erosion is a global environmental problem. The rapid monitoring of the coverage changes in and spatial patterns of photosynthetic vegetation (PV) and non-photosynthetic vegetation (NPV) at regional scales can help improve the accuracy of soil erosion evaluations. Three deep learning semantic segmentation models, DeepLabV3+, PSPNet, and U-Net, are often used to extract features from unmanned aerial vehicle (UAV) images; however, their extraction processes are highly dependent on the assignment of massive data labels, which greatly limits their applicability. At the same time, numerous shadows are present in UAV images. It is not clear whether the shaded features can be further classified, nor how much accuracy can be achieved. This study took the Mu Us Desert in northern China as an example with which to explore the feasibility and efficiency of shadow-sensitive PV/NPV classification using the three models. Using the object-oriented classification technique alongside manual correction, 728 labels were produced for deep learning PV/NVP semantic segmentation. ResNet 50 was selected as the backbone network with which to train the sample data. Three models were used in the study; the overall accuracy (OA), the kappa coefficient, and the orthogonal statistic were applied to evaluate their accuracy and efficiency. The results showed that, for six characteristics, the three models achieved OAs of 88.3–91.9% and kappa coefficients of 0.81–0.87. The DeepLabV3+ model was superior, and its accuracy for PV and bare soil (BS) under light conditions exceeded 95%; for the three categories of PV/NPV/BS, it achieved an OA of 94.3% and a kappa coefficient of 0.90, performing slightly better (by ~2.6% (OA) and ~0.05 (kappa coefficient)) than the other two models. The DeepLabV3+ model and corresponding labels were tested in other sites for the same types of features: it achieved OAs of 93.9–95.9% and kappa coefficients of 0.88–0.92. Compared with traditional machine learning methods, such as random forest, the proposed method not only offers a marked improvement in classification accuracy but also realizes the semiautomatic extraction of PV/NPV areas. The results will be useful for land-use planning and land resource management in the areas.

Context Severe soil erosion in the Chinese Loess Plateau and the resulting high sediment yield of the Yellow River have been important research topics. Aims Understanding the impacts of vegetation types on soil hydro-physical properties is essential for understanding regional runoff-sediment changes, soil and water conservation, and revegetation. Methods Three main plantation covers of the study area [natural restoration grassland (NG), artificial Prunus armeniaca forest (AP), and artificial Hippophae rhamnoides shrubland (AH) with 15 years of restoration] and Sorghum bicolor agricultural land as control (CK), were selected to compare their soil hydro-physical properties and infiltration capacity in the soil profile. Key results The bulk density was lower, and soil organic matter (SOM), the proportion of macro-aggregates (>5 mm), mean weight diameter (MWD) of water-stable aggregates, and the initial infiltration and stable infiltration rate were higher in the AH plot compared to CK and the other two plots. The impacts of vegetation restoration on soil properties were mainly in the 0–60 cm layer. Infiltration rates changed mainly within 5 h and basically stabilised within 10 h, with even shorter times to reach stable infiltration in CK. The initial and stable infiltration rates were significant positively correlated (P

Investigations of the formation mechanisms of flood peaks in small catchments facilitate flood prediction and disaster prevention under extreme rainstorms. However, there have been few studies on the responses of flood peaks to land use landscape patterns using field surveys during extreme rainstorm events. Based on field data from 17 small catchments near the rainstorm center of Typhoon Lekima, 7 landscape indices were chosen. The flood peak and its sensitivity to the land use landscape were investigated by combining remote sensing interpretation and related analysis. The conclusions are as follows: (1) The peak discharge of the small catchment was 2.36–56.50 m3/s, the peak modulus was 8.00–48.89 m3/(s·km2), and the flood index K ranged from 3.61 to 4.55. (2) Under similar rainfall conditions, the flood peak modulus, K and the proportion of sloping cropland had significantly positive correlations (p

More frequent extreme rainfall events associated with global climate change cause greater challenges for soil conservation. Severe erosion occurs on many unpaved roads since these structures create important water flow paths during heavy storms. The present research aimed to investigate the intensity and influencing factors of unpaved road erosion under varied land use and management conditions (sloping cropland, terraced cropland, forest & grass). The erosion occurred in the watersheds contributing runoff water to roads after the greatest rainfall event recorded in the mountain area of northern China caused by Typhon Lekima. The research was conducted in an agricultural-forest-dominated watershed based on field investigation and UAV-based image analysis. A road erosion level classification standard was given according to the occurrence of rills, ephemeral gullies, and gullies. Significant erosion happened on 67% of the unpaved roads; 42% of them suffered moderate to severe erosion in which ephemeral gullies or gullies developed. The average erosion amount from these roads was 2280.75 t ha-1 and was significantly influenced by the watershed land use type and management. The dominant factor governing unpaved road erosion associated with terraced cropland was vegetation coverage on roads. Drainage area was the most important factor for road erosion in sloping cropland and forest & grass land, and road gradient was also a critical factor. Terraces, and forest & grass in drainage areas significantly reduced unpaved road erosion by 85% and, 47%, respectively, compared to sloping cropland. More integrated measures should be used to prevent unpaved road erosion. The results of this research can be applied to road protection against erosion in heavy storms.

More than 40 million tons of thermosetting plastics are produced annually and 70% of those are epoxy polymers. Propylpyrogallol made from genetically modified high-S lignin provides a pathway for making renewable thermoset plastics.

Hepatitis E, a significant global public health issue in China, is caused by sporadic infections with regional hepatitis E virus (HEV) genotypes 1, 3, and 4. To date, most immunoassays currently used to test human sera for the presence of anti-HEV antibodies cannot identify HEV at the genotype level. However, such information would be useful for identifying the source of infecting virus. Therefore, here we describe the development of a competitive enzyme-linked immunosorbent assay (ELISA) for detecting anti-genotype 1 HEV antibodies in human sera. Using recombinant genotype 1 HEV ORF3 protein as immunogen, traditional hybridoma technology was employed to generate seven monoclonal antibodies (mAbs), of which two mAbs specifically reacted with the immunogen. One of these two mAbs, 1D2, was labeled with horseradish peroxidase (HRP) for use in competitive ELISA (cELISA). After cELISA optimization using a checkerboard assay design, the amount of ORF3SAR−55 as coating antigen (100 ng/well), HRP-1D2 mAb concentration (1 μg/mL), and test serum dilution (1:10) were selected and a result ≥ 19.5 was used as the cutoff for a positive result. Importantly, cross-genotype cELISA results indicated that the cELISA could not detect anti-genotype 3 rabbit and 4 swine HEV antibodies. Moreover, human sera confirmed as negative for anti-HEV antibodies using the commercial ELISA kit were all negative via cELISA. However, because the commercial ELISA kit detects anti-all genotypes HEV antibodies and the cELISA only detects anti-genotype 1 HEV antibodies, the consistence rate of two assays detecting positive sera is low. In summary, here a cELISA for detecting anti-genotype 1 HEV antibodies was developed for use in epidemiological investigations of genotype 1 HEV infections in humans. • Seven mAbs were produced using genotype 1 HEV ORF3 protein as immunogen. • One mAb that specifically bound to genotype 1 HEV ORF3 protein was selected and labeled for use in a cELISA to detect anti-genotype 1 HEV antibodies. • The competitive ELISA developed here will aid clinical diagnosis of HEV infections and will be useful for large-scale serological testing of genotype 1 HEV infections in humans.

The Chinese Loess Plateau, characterized by severe soil erosion and a vulnerable environment, is highly sensitive to extreme weather events. Understanding the changing patterns of extreme precipitation events and the associated rainfall erosivity, as well as their effects on the soil erosion and sediment delivery, is essential to the application of planning and ecological restoration on the Loess Plateau. In total, 100 meteorological stations with high-quality daily data spanning from 1957 to 2018 were used to extract eight indices to evaluate the variations in extreme precipitation and the associated rainfall erosivity, and to identify the contribution of extreme precipitation to rainfall erosivity and thus to sediment delivery. The annual extreme precipitation from six of eight indices all exhibited insignificant decreases in the study area. The average annual rainfall erosivity was 1159 MJ mm ha−1 h−1 year−1, with a slight decreasing rate of − 3.16 MJ mm ha−1 h−1 year−1 over a 10-year period. The rainfall erosivity presented a staged descending change ranging from the 1960s to the late 1990s, but a promptly ascending change since 2000. These variations in extreme precipitation and the associated rainfall erosivity in the region were very likely to be affected by the changing pattern of the East Asian summer monsoon. The annual precipitation from three kinds of extreme events, namely, maximum 5-day precipitation (RX5d), heavy precipitation (R20), and very wet day precipitation (R95p), contributed 60–90% of the annual rainfall erosivity, respectively. Compared with the reference period (1957–1979), the rainfall erosivity resulting from extreme precipitation events contributed less to the dramatic reduction in sediment delivery on the Loess Plateau in the periods of 1980 to 1999 and 2000 to 2018. The results imply a reduced impact of rainfall erosivity and increased human intervention on sediment delivery on the Loess Plateau in the last 60 years. These findings are useful in understanding the processes of ecohydrology and soil erosion delivery in the region.

Hepatitis E virus (HEV) is thought to be a zoonotic pathogen that causes serious economic loss and threatens human health. However, there is a lack of efficient antiviral strategies. As a more promising tool for antiviral therapy, nanobodies (also named single-domain antibodies, sdAbs) exhibit higher specificity and affinity than traditional antibodies. In this study, nanobody anti-genotype four HEV open reading frame 2 (ORF2) was screened using phage display technology, and two nanobodies (nb14 and nb53) with high affinity were prokaryotically expressed. They were identified to block HEV ORF2 virus like particle (VLP) sp239 (aa 368–606) absorbing HepG2 cells in vitro. With the previously built animal model, the detection indicators of fecal shedding, viremia, seroconversion, alanine aminotransferase (ALT) levels, and liver lesions showed that nb14 could completely protect rabbits from swine HEV infection, and nb53 partially blocked swine HEV infection in rabbits. Collectively, these results revealed that nb14, with its anti-HEV neutralizing activity, may be developed as an antiviral drug for HEV.

Circulation of influenza A virus (IAV), especially within poultry and pigs, continues to threaten public health. A simple and universal detecting method is important for monitoring IAVs infection in different species. Recently, nanobodies, which show advantages of easy gene-editing and low cost of production, are a promising novel diagnostic tool for the monitoring and control of global IAVs. In the present study, five nanobodies against the nucleoprotein of H9N2 IAV were screened from the immunized Bactrian camel by phage display and modified with horseradish peroxidase (HRP) tags. Out of which, we determined that H9N2-NP-Nb5-HRP can cross-react with different subtypes of IAVs, and this reaction is also blocked by positive sera for antibodies against different IAV subtypes. Epitope mapping showed that the nanobody-HRP fusion recognized a conserved conformational epitope in all subtypes of IAVs. Subsequently, we developed a nanobody-based competitive ELISA (cELISA) for detecting anti-IAV antibodies in different species. The optimized amount of coating antigen, as well as dilutions of the fusion and testing sera were 100 ng/well, 1:4,000, and 1:10, respectively. The time for operating the cELISA was approximately 35 min. The cELISA showed high sensitivity, specificity, reproducibility, and stability. Additionally, we found that the cELISA and hemagglutination inhibition (HI) test showed a consistency of 100% and 87.91% for clinical and challenged chicken sera, respectively. Furthermore, the agreement rates were 90.4% and 85.7% between the cELISA and commercial IEDXX ELISA kit. Collectively, our developed nanobody-HRP fusion-based cELISA is an ideal method for monitoring IAV infection in different species.

Soil thickness determines the soil productivity in the black soil region of northeast China, which is important for national food security. Existing information on the spatial variation of black soil thickness is inadequate. In this paper, we propose a model framework for spatial estimation of the black soil thickness at the watershed scale by integrating field observations, unmanned aerial vehicle variations of topography, and satellite variations of vegetation with the aid of random forest. We sampled 141 sample profiles over a watershed and identified the black soil thickness based on indices of the mollic epipedon. Topographic variables were derived from a digital elevation model and vegetation variables were derived from Landsat 8 imagery. Random forest was used to determine the relationship between black soil thickness and environmental variables. The resulting model explained 61% of the black soil thickness spatial variation, which was more than twice that of traditional interpolation methods (ordinary kriging, universal kriging and inverse distance weighting). Topographic variables contributed the most toward explaining the thickness, followed by vegetation indices. The black soil thickness over the watershed had a clear catenary soil pattern, with thickest black soil in the low depositional areas and thinnest at the higher elevations that drain into the low areas. The proposed model framework will improve estimates of soil thickness in the region of our study.

The dry-hot valley region in China is one of the most severely affected soil erosion areas in the world; however, little research has been conducted on sediment source contributions for various land uses during rainfall events. In this work, we collected sediment samples during a rainstorm in four types of land-use areas in the Yuanjiang dry-hot valley region of China. Results showed that gullies are the primary source of sediments in all catchment areas, and the contributions varied between 43.6% and 93.9%, with an average of 64.9%. This was followed by farmlands (21.3% to 30.4% with an average of 25.9%) and then fruit forests (6.1% to 36.5% with an average of 20.5%). Natural forests had the lowest sediment contribution as their contribution varied between 0.6% and 6.1%, with an average of only 3.3%. During runoff-induced erosion and sedimentation, the sediment contributions of gullies decreased initially and then increased. The sediment contribution of potential sediment sources located on slopes (i.e., fruit forests, natural forests, and farmlands) initially increased over time, and then declines were detected after a certain point

Soil erosion is one of the most severe global environmental problems, and soil erosion surveys are the scientific basis for planning soil conservation and ecological development. To improve soil erosion sampling survey methods and accurately and rapidly estimate the actual rates of soil erosion, a Pan-Third Pole region was taken as an example to study a methodology of soil erosion sampling survey based on high-spatial-resolution remote sensing images. The sampling units were designed using a stratified variable probability systematic sampling method. The spatiotemporal characteristics of soil erosion and conservation were taken into account, and finer-resolution freely available and accessible images in Google Earth were used. Through the visual interpretation of the free high-resolution remote sensing images, detailed information on land use and soil conservation measures was obtained. Then, combined with the regional soil erosion factor data products, such as rainfall-runoff erosivity factor (R), soil erodibility factor (K), and slope length and steepness factor (LS), the soil loss rates of some sampling units were calculated. The results show that, based on these high-resolution remote sensing images, the land use and soil conservation measures of the sampling units can be quickly and accurately extracted. The interpretation accuracy in 4 typical cross sections was more than 80%, and sampling accuracy, described by histogram similarity in 11 large sampling sites, show that the landuse of sampling uints can represent the structural characteristics of regional land use. Based on the interpretation of data from the sample survey and the regional soil erosion factor data products, the calculation of the soil erosion rate can be completed quickly. The calculation results can reflect the actual conditions of soil erosion better than the potential soil erosion rates calculated by using the coarse-resolution remote sensing method.

Soil erosion is a major environmental problem in China. Planning for soil erosion control requires accurate soil erosion rate and spatial distribution information. The aim of this article is to present the methods and results of the national soil erosion survey of China completed in 2011. A multi-stage, unequal probability, systematic area sampling method was employed. A total of 32,948 sample units, which were either 0.2–3 km2 small catchments or 1 km2 grids, were investigated on site. Soil erosion rates were calculated with the Chinese Soil Loss Equation in 10 m by 10 m grids for each sample unit, along with the area of soil loss exceeding the soil loss tolerance and the proportion of area in excess of soil loss tolerance relative to the total land area of the sample units. Maps were created by using a spatial interpolation method at national, river basin, and provincial scales. Results showed that the calculated average soil erosion rate was 5 t ha−1 yr−1 in China, and was 18.2 t ha−1 yr−1 for sloped, cultivated cropland. Intensive soil erosion occurred on cropland, overgrazing grassland, and sparsely forested land. The proportions of soil loss tolerance exceedance areas of sample units were interpolated through the country in 250 m grids. The national average ratio was 13.5%, which represents the area of land in China that requires the implementation of soil conservation practices. These survey results and the maps provide the basic information for national conservation planning and policymaking.

As one of the important indicators reflecting the regional ecological environment, fractional vegetation coverage is significant for regional eco-environmental protection and sustainable utilization of resources. To understand changes in the ecological environment of the ecologically fragile areas in the Loess Plateau affected by “Grain for Green” Program and its main driving forces in the past two decades, this study taking Yulin City as a typical example of the fragile ecological environment on the Loess Plateau, to analyze spatial-temporal variations of the vegetation coverage in Yulin City during the past two decades based on the pixel dichotomy model with vegetation index, using univariate linear regression methods. The dominant factors and interaction between factors influencing the interannual changes and spatial distribution of vegetation coverage are analyzed using the partial correlation analysis and geographic detector methods during the different period in “Grain for Green” Program. Results showed that: (1) The vegetation coverage in Yulin City significantly increased (S = 0.011, p < 0.01) from 2001 to 2020. The vegetation coverage during the construction periods (2001-2010) increased significantly (S = 0.013, p 0.05). (2)The spatial distribution of vegetation coverage in Yulin City decreased from east to west from 2001 to 2020. The vegetation coverage of all counties (districts) in Yulin City shows an overall increasing trend, among which the eastern part of Yulin City has a more significant growth trend. However, the proportion of area in the construction periods (82.1%) was larger than that in the consolidation periods (58.0%). (3) The cumulative area of the Grain for Green Program was the dominant factor in the construction periods, while it was rainfall in the consolidation period. (4) Soil texture, rainfall, and land use type mainly affected the spatial distribution of vegetation coverage from 2001 to 2020. Soil texture was closely related to changes in the vegetation coverage both in the construction and consolidation periods. The spatial heterogeneity of vegetation distribution and the interaction between the main influencing factors provides a scientific basis for the precise implementation of ecological restoration measures.

Background Hepatitis E virus (HEV) genotypes 3 and 4 are zoonotic. In this study, HEV infection in laboratory Bama miniature pigs in Sichuan Province of China was investigated. Firstly, one hundred rectal swabs were collected for HEV RNA testing, and chose positive samples for sequence analysis. Concurrently, for pathogenicity study, six healthy Bama miniature pigs were randomly divided into two groups of 3 pigs each. A total of 500 μL of HEV stock (positive fecal samples identified in this study) was inoculated intravenously into each pig in the experimental group, and the three pigs in the other group served as negative controls. Serum and fecal samples were collected at 1 to 10 weeks post-inoculation (wpi) for alanine aminotransferase (ALT) levels, anti-HEV antibodies and HEV RNA detection, respectively. During necropsies, liver lesions and HEV antigen in liver were observed at 10 wpi. Results The rate of fecal sample HEV RNA-positivity was 12% (12/100). Sequence comparisons indicated that partial ORF1 and ORF2 gene sequences of this isolate shared highest identities with corresponding sequences of genotype 4a HEV isolates (81.4%-96.1% and 89.9%-97.1%, respectively). Phylogenetic tree analysis further demonstrated that sequences of this isolate clustered together with sub-genotype 4a HEV isolate sequences. Experimentally, the pathogenicity of Bama miniature pigs infected with this isolate exhibited viremia, fecal virus shedding, seroconversion, ALT level increasing, liver lesions and HEV antigen in liver. Conclusions This is the first study to confirm that HEV is currently circulating in laboratory Bama miniature pigs in China and this isolate can successfully infect Bama miniature pigs experimentally. More importantly, this study suggested HEV screening of laboratory pigs should be conducted to prevent research personnel from acquiring zoonotic HEV infections.

Avian hepatitis E virus (HEV) causes liver diseases and multiple extrahepatic disorders in chickens. However, the mechanisms involved in avian HEV entry remain elusive. Herein, we identified the RAS-related protein 1b (Rap1b) as a potential HEV-ORF2 protein interacting candidate. Experimental infection of chickens and cells with an avian HEV isolate from China (CaHEV) led to upregulated expression and activation of Rap1b both in vivo and in vitro. By using CaHEV capsid as mimic of virion to treat cell in vitro, it appears that the interaction between the viral capsid and Rap1b promoted cell membrane recruitment of the downstream effector Rap1-interacting molecule (RIAM). In turn, RIAM further enhanced Talin-1 membrane recruitment and retention, which led to the activation of integrin α5/β1, as well as integrin-associated membrane protein kinases, including focal adhesion kinase (FAK). Meanwhile, FAK activation triggered activation of downstream signaling molecules, such as Ras-related C3 botulinum toxin substrate 1 RAC1 cell division cycle 42 (CDC42), p21-activated kinase 1 (PAK1), and LIM domain kinase 1 (LIMK1). Finally, F-actin rearrangement induced by Cofilin led to the formation of lamellipodia, filopodia, and stress fibers, contributes to plasma membrane remodeling, and might enhance CaHEV virion internalization. In conclusion, our data suggested that Rap1b activation was triggered during CaHEV infection and appeared to require interaction between CaHEV-ORF2 and Rap1b, thereby further inducing membrane recruitment of Talin-1. Membrane-bound Talin-1 then activates key Integrin-FAK-Cofilin cascades involved in modulation of actin kinetics, and finally leads to F-actin rearrangement and membrane remodeling to potentially facilitate internalization of CaHEV virions into permissive cells. IMPORTANCE Rap1b is a multifunctional protein that is responsible for cell adhesion, growth, and differentiation. The inactive form of Rap1b is phosphorylated and distributed in the cytoplasm, while active Rap1b is prenylated and loaded with GTP to the cell membrane. In this study, the activation of Rap1b was induced during the early stage of avian HEV infection under the regulation of PKA and SmgGDS. Continuously activated Rap1b recruited its effector RIAM to the membrane, thereby inducing the membrane recruitment of Talin-1 that led to the activation of membrane α5/β1 integrins. The triggering of the signaling pathway-associated Integrin α5/β1-FAK-CDC42&RAC1-PAK1-LIMK1-Cofilin culminated in F-actin polymerization and membrane remodeling that might promote avian HEV virion internalization. These findings suggested a novel mechanism that is potentially utilized by avian HEV to invade susceptible cells.

The black soil region in northeastern China is one of the most important grain production areas in the country, and plays a key role in food security. Large lands have been brought into cultivation in the last 100 years. Because these lands have lesser slope gradients compared to those in the loess plateau and other regions in China, soil erosion has been ignored in this area for a long time. Few soil conservation practices have been implemented. Serious soil erosion problems due to long slope lengths have been identified based on recent research and observations in the study area. The government has realized the necessity and urgency of soil conservation. However, to create policies and plans for black soil conservation, questions such as how much of the black soil region, and where in the region, erosion is a problem must be addressed. Currently, the black soil region of northeastern China is regarded as having a total area of 1.09 million square kilometers, including Heilongjiang, Jilin, the north part of Liaoning, and the east part of Inner Mongolia, in which there are also many non-black soils in mountain regions of Daxingan, Xiaoxingan, and Changbaishan. Therefore, it is difficult to determine precisely the conservation priorities for this large area. In this study, the black soils were defined and their concentrated area was delineated in northeastern China. The black soils were defined as soils with the “mollic epipedon”, which were classified as Isohumosols in Chinese Soil Taxonomy or Mollisols in the USDA Soil Taxonomy, and classified as Phaezoems, Chernozems, Kastanozems and Grayzems soils according to the Genetic Soil Classification of China (GSCC). The region dominated by these four soils in GSCC was defined as the black soil region. Because Phaezoems and Chernozems have higher organic matter contents and deeper mollic epipedon depths, and are distributed in the center of the study area, these two soils were defined as the typical black soil, and their dominate area was defined as the typical black soil region. A soil map in the scale of 1:1000000, made from the second national soil survey, was used with ArcGIS 10.2 software to delineate both black soil and typical black soil regions. A method called “central gravitational agglomeration” was developed. All of the soil polygons were selected, and the farthest and the smallest polygon were merged into its closest adjacent one if its radius was larger than the distance between it and its closest one. Otherwise it was abandoned. The same process was repeated until only a few small polygons were left and a regional outline appeared. Four soils were used to determine the exact boundaries of the black soil region, and two soils were used to determine the exact boundaries of the typical black soil region. The results showed that the area of the black soil region was 556000 km2, including 146 counties in which 33.0% was cultivated land. The area of the typical soil region was 333000 km2, including 138 counties in which 50.2% was cultivated land. Due to the long slopes, the soil erosion rate from the cropland with slope greater than 0.25° is estimated to be larger than soil loss tolerance of 200 t/km2. The cultivated lands with slope greater than 0.25° were regarded as sloped cultivated land or sloped cropland, which totaled 89000 km2, or 16.0% of the total land for the black soil region, and 78000 km2, or 23.4% of the total land for the typical black soil region. The sloped cultivated land in both the black soil region and typical black soil region should be targeted as key areas for soil erosion control in northeastern China.

Check dams are widely distributed and abundant on the Chinese Loess Plateau and play an important role both in reducing damage from flash floods and in retaining sediment. Some check dams are destroyed either partially or fully during rainstorms. The investigation of the actual damage caused to check dams as a result of specific rainstorm floods is of great value for analyzing their effects and failure modes, and is also helpful for proposing a reasonable approach for their improvement. The “7.26” extreme rainstorm event on July 25 and 26, 2017, in Yulin in northern Shaanxi Province, China, resulted in serious infrastructural damage and economic losses. This study reports on a detailed investigation undertaken between August 27 and October 28, 2017, of the causes and severity of the damage to the check dams in the Chabagou watershed. The results showed that out of a total of 572 check dams surveyed, 63.6% were destroyed and 9.3% were damaged. The mean dam opening was 4.8 m wide and 3.4 m deep, while the mean water culvert was 1.7 m wide and 2 m deep. The main causes of the damage were as follows: (1) the flood return period exceeded the dam design standards, (2) 94.1% of the check dams lacked a spillway, and (3) the main land use types on the check dams were farmland and bare soil. Based on the findings of this study, the following recommendations are made: (1) improve the existing design standards for check dams, (2) build additional spillways and maintain existing spillways in a timely fashion, and (3) encourage the development of natural grass and shrub land as the best land use type on check dams.

A physical mixture of Ru/C and Nb2O5 is an effective catalyst for upgrading lignin monomers under low H2 pressure at 250 °C to a clean cut of hydrocarbon liquid fuels. The reaction solvent is water with a small amount of methanol additive. Hydrodeoxygenation (HDO) was evaluated using dihydroeugenol (DHE) as an exemplary lignin monomer model. Under optimized conditions, 100% conversion of DHE and very high selectivity to propyl cyclohexane (C9 hydrocarbon) was achieved. Nb2O5 was prepared at a low temperature (450 °C) and was shown to contain acid sites that enhance the production of fully deoxygenated products. The methanol additive serves as a hydrogen source for the Ru/C catalysed reduction of the aromatic ring. In addition, when a substrate mixture of DHE, isoeugenol and 4-allylsyringol simulating lignin products was employed, 100% conversion to propyl cyclohexane (76%) and propyl benzene (24%) was observed, thereby suggesting the general applicability of this catalyst system for funneling lignin monomers into a clean cut of hydrocarbon liquid fuels. This study sheds light on the function of each catalyst component and provides a simple and green utilization of biomass monomers as a feedstock for renewable hydrocarbon fuels.

Salmonella are major pathogens that cause foodborne diseases. In this work, a broad-spectrum Salmonella nanobody-01 (Nb-01) was isolated and applied in the development of a streptavidin-bridged sandwich ELISA (SAB-ELISA) for simultaneously identifying five Salmonella serovars, including Salmonella Enteritidis (S. Enteritidis), Salmonella Typhimurium (S. Typhimurium), Salmonella London (S. London), Salmonella Paratyphi B (S. Paratyphi B) and Salmonella Hadar (S. Hadar). In this work, streptavidin (SA) was utilized as a scaffold to directionally immobilize biotinylated nanobody (BiNb) and Salmonella was detected by phage-displayed nanobodies. The SAB-ELISA can be accomplished within 180 min with a limit of detection (LOD) of 6.31 × 10

Avian hepatitis E virus (avian HEV) increases poultry mortality and decreases egg production, leading to huge economic losses worldwide. However, there is no effective serological test for avian HEV. Researchers previously created a testing platform using the nanobody (Nb)-horseradish peroxidase (HRP) fusion protein as an ultrasensitive probe to develop competitive ELISA (cELISA) to detect antibodies against different animal viruses. In this study, a rapid and reliable cELISA was developed to test for antibodies against avian HEV using the same platform. Six anti-avian HEV capsid protein nanobodies were selected from an immunized Bactrian camel using phage display technology. The avian HEV-Nb49-HRP fusion protein was expressed and used as a probe for developing a cELISA assay to test for avian HEV antibodies. The cut-off value of the developed cELISA was 22.0%. There was no cross-reaction with other anti-avian virus antibodies, suggesting that the cELISA had good specificity. The coefficients of variation were 0.91% to 4.21% (intra-assay) and 1.52% to 6.35% (inter-assay). Both cELISA and indirect ELISA showed a consistency of 86.7% (kappa = 0.738) for clinical chicken serum samples, and coincidence between cELISA and Western blot was 96.0% (kappa = 0.919). The epitope recognized by Nb49 was located in aa 593-604 of the avian HEV capsid protein, and the peptide (TFPS) in aa 601-604 was essential for binding. The novel cELISA is a saving cost, rapid, useful, and reliable assay for the serological investigation of avian HEV. More importantly, the peptide TFPS may be crucial to immunodominant antigen composition and protection.

Image fusion method is an algorithm that synthesizes images from different sources into a new image. The advantage of image fusion technology is that different image information presented by multi-source sensors can complement and improve each other to extract the effective information in the source image. It can also obtain a more effective and richer image with description information. According to the technical methods of image fusion, an improved image fusion method for fast non-downsampled contourlet transform (NSCT) was selected for handheld. The source infrared image and source low-light image collected by the observer were image fusion. In this method, the scale filter and the directional filter were convolved respectively in the composition of image decomposition and reconstruction to reduce the number of iterations of image decomposition and reconstruction, improve the efficiency of algorithm operation, and ensure that the system worked in real time.

Background: Nanobodies are the third generation of genetically-engineered antibodies, possessing advantages of small molecular weight, simple genetic engineering, and low production cost for promising diagnostic application. In this study, a competitive ELISA (cELISA) using nanobody-horseradish peroxidase (HRP) fusion protein was utilized as an ultrasensitive probe for the first time to detect antibodies against genotype 2 porcine reproductive and respiratory syndrome virus (PRRSV). In addition, a platform for easily producing the nanobody-HRP fusion protein against PRRSV was designed and developed. Results: In the present study, three nanobodies against the PRRSV-N protein were screened by Camel immunization, library construction, and phage display. Subsequently, a recombinant HEK293S cell line stably secreting nanobody-HRP fusion protein against PRRSV-N protein was successfully designed and constructed using the lentivirus transduction assay. Using the cell lines, the fusion protein was easily produced. Then, a novel cELISA was developed using the nanobody-HRP fusion protein for detecting the antibodies against genotype 2 PRRSV in pig sera, exhibiting a cut‑off value of 23.19% and good sensitivity (100%), specificity, and reproducibility. The compliance rate of cELISA with a commercial IDEXX ELISA kit was 96.4%. By testing the sequential sera from the challenged pigs, the results showed that the sensitivity of cELISA was higher than the commercial IDEXX ELISA kit. In addition, the commercial IDEXX ELISA kit can be combined with the developed cELISA for the differential detection of antibodies against genotype 1 and 2 PRRSV in pig sera.Conclusions: By screening the three nanobodies against the genotype 2 PRRSV-N protein, a recombinant HEK293S cell line stably secreting nanobody-HRP fusion protein against PRRSV-N protein was developed (Scheme 1a). Subsequently, a cELISA was developed for detecting the antibodies against genotype 2 PRRSV using the fusion protein and demonstrated high sensitivity, specificity, and reproducibility (Scheme 1b). More importantly, the production of the fusion protein using the developed platform is simple and low cost.

The natural environment provides material essentials for human survival and development. The characteristics, processes, regional differentiation and forcing mechanisms of the elements of the natural environment (e.g. geomorphology, climate, hydrology, soil, etc.) are the main objects of research in physical geography. China has a complex natural environment and huge regional differentiation and therefore it provides outstanding reserach opportunities in physical geography. This review summarizes the most important developments and the main contributions of research in the physical geography and human living environment in China during the past 70 years. The major topics addressed are the uplift of the Tibetan Plateau and the evolution of its cryosphere, the development of fluvial systems, the acidification of the vast arid region of the Asian interior, variations in the monsoon and westerly climate systems on multiple timescales, the development of lakes and wetlands, the watershed system model, soil erosion, past human-environment interactions, biogeography, and physical geographic zonality. After briefly introducing international research developments, we review the history of research in physical geography in China, focusing on the major achievements and major academic debates, and finally we summarize the status of current research and the future prospects. We propose that in the context of the national demand for the construction of an ecological civilization, we should make full use of the research findings of physical geography, and determine the patterns and mechanisms of natural environmental processes in order to continue to promote the continued contribution of physical geography to national development strategies, and to further contribute to the theory of physical geography from a global perspective.

Compound erosion of wind and water is a serious global environmental problem, and the relative magnitude of water versus wind erosion has important implications for future studies and soil conservation practices. However, currently, field measurements of compound erosion are rarely reported, probably due to the lack of generally accepted wind erosion measurement methods. In this study, an agricultural field at the northern end of the Loess Plateau was selected to measure the compound erosion from 2012 to 2014, in which water erosion was measured by runoff plots, while wind erosion was measured using BSNE samplers. The results indicated that: 1) annual water erosion ranged from 8.1 to 89.4 t ha−1 a−1 with a mean of 43.8 t ha−1 a−1, while wind erosion ranged from 0.82 to 2.12 t ha−1 a−1 with a mean of 1.58 t ha−1 a−1; 2) water erosion primarily occurred in the summer, while wind erosion occurred in the spring, and substantial variability was revealed on both the interannual and intra-annual scales for both erosion processes; 3) the compound erosion was temporally alternated and spatially overlaid in the selected field, and wind erosion only accounted for 3% of the compound erosion. Although water erosion greatly exceeded wind erosion for the selected agricultural field, the need for measuring and monitoring over a longer period to cover the natural variability of weather conditions is highlighted. The relative magnitude of water versus wind erosion was quantified, but more relevant studies are needed, since these studies usually have important implications for future studies and soil conservation practices.

Reliable and efficient erosion measurement techniques are essential for monitoring soil erosion rates and patterns, understanding soil erosion mechanisms and developing erosion prediction models. Existing erosion measurement techniques, typically including erosion pins, 3D laser scanners and erosion tracers, have some limitations in practice. A new in situ technique, called the magnetic layer detection (MLD) method, is introduced in this paper. The MLD method determines superficial soil layer thickness (SLT) by detecting the depth of an underground artificial magnetic layer (ML) using a magnetic susceptibility (MS) field probe. It enables a shift from rapid MS measurement to soil erosion or deposition quantification. The results of simulated soil profiles showed the relationship between SLT and volume MS of a target ML exactly followed a universal exponential equation, not sensitive to soil type and ML magnetism level. The theoretical analysis based on the optimally fitted curves showed the accuracy of the MLD method is

The laser diffraction method (LDM) has been increasingly applied for quantifying soil particle size distribution (PSD), owing to its advantages of rapid analysis, high reproducibility, and continuous PSD measurement for a wide range of size fractions. However, some ambiguities exist regarding the comparability of results with those obtained using other classical methods. The objective of the current study was to evaluate LDM-derived PSDs via comparisons with PSDs obtained with the standard sieve–pipette method (SPM) and from the absolute method of microscopy. A total of 277 soil samples were collected at different soil depths in a typical cropland in the northeast mountainous region of Beijing and analyzed with both SPM and LDM. Due to time and labor constraints, scanning electron microscopy (SEM) was performed on 100 samples randomly selected for the PSDs within the clay fraction withdrawn by SPM. The results manifested on the average 18.9% underestimation of clay content and 25.3% overestimation of silt content by LDM compared to SPM. These disagreements directly caused the shifts of soil texture class in 44.8% of the soil samples. Significant linear regression equations were generated to convert LDM–derived sand and silt contents to SPM–derived ones (p < 0.01). The linear conversions for the clay content were only significant for the calibration samples, but possessed negative coefficients of determination for the validation set. According to SEM, silt-sized particles were wrongly included in the clay fraction identified by SPM. Eliminating such particles, the clay contents corrected by SEM were significantly lower when assuming the shape of clay particles < 2 µm as plates or discs with constant thickness–diameter ratio of 1/10, and higher when considering the clay particles as spheres for volume calculation, in contrast to those measured by LDM (P < 0.01). Detailed volume-based PSDs within the clay fraction were further compared between SEM and LDM, revealing dissimilar PSD patterns but statistically similar median particle diameters. These findings suggest the effectiveness of LDM in soil PSD determination. Future work is needed to systematically quantify the impact of other possible factors such as clay mineralogy and refractive index on LDM-derived PSDs.

Saturated hydraulic conductivity (Kₛ) usually varies at multiple scales in space, as affected by different soil and environmental processes operating at diverse scales. Identifying spatial process relationships can be challenging due to overlapping of underlying processes at different scales. The objective of this study was to evaluate noise-assisted multivariate empirical mode decomposition (NA-MEMD) for characterizing Kₛ variability and depicting its scale-dependent relationships with different soil properties and environmental factors. At an interval of 10 km along an 860-km south-north transect across the Loess Plateau of China, Kₛ, bulk density, soil organic carbon content, sand and clay contents at three depths of 0 to 10, 10 to 20 and 20 to 40 cm were investigated as well as four environmental factors of elevation, slope gradient, annual precipitation and temperature. Decomposed into different intrinsic mode functions (IMFs) and residues by NA-MEMD, Kₛ at all depths were found to vary at the smallest scale of 29 km mainly, corresponding to IMF1s, which manifested 33.0 to 48.1% of the total Kₛ variance. The small-scale variations of Kₛ reflected not only in IMF1s but also in IMF2s and IMF3s were dominated by soil properties especially bulk density, and the large-scale variations corresponding to IMF4s and IMF5s were controlled by environmental factors in general. For each depth, Kₛ at the scale of investigation was estimated by adding all the IMFs and residue derived from the factor components at equivalent scales using multiple linear regression (MLR). Such Kₛ estimations after NA-MEMD evidently outperformed the MLR before NA-MEMD by explaining additional 9.4 to 18.7% of the total Kₛ variance, but underperformed the artificial neural network and state-space approach also implemented on undecomposed spatial series of Kₛ and its underlying factors. NA-MEMD serves as a useful tool for Kₛ characterization and its incorporation with nonlinear functions or spatial interactions with impact factors is suggested for the estimation of Kₛ and other soil processes.

Various conservation practices have been used to control soil erosion in cropland which makes assessing the effects of soil conservation more important. Northeastern China is an important crop-producing regions, with severe soil erosion. In the study, 110 runoff plot-year observations from seven experimental stations distributed over the region were used to assess the effects of local conservation practices on soil erosion, using a simplified USLE. Under the assumption that there were no significant differences in rainfall erosivity and soil erodibility in the study area under the “no practice scenario”, we described a simplified linear model based slope steepness and soil loss rate. The Jixing watershed was selected as a case study to test the model. The results indicate that the derived model can be used in the NE region of China for conservation assessment. The P factor values, related to main soil conservation practices, were derived from the observed plot-year data. The average values of P factor were around 0.01 to 0.35, which were low enough to justify their conservation effects of implementation through the assessment. Comparing to the conventional slope ridging tillage, the conservation rates of terraces, strip ridging, orchards and agro-forestry in the Jixing Watershed were 0.57, 0.6, 1.07, and 0.62 mm/ha, respectively, obtained by the assessment method in the study case. The paper neglected the seasonal variation which should be grouped to the C factor for the annual data and discussed the limitations of the assessment model for application.

Hepatitis E virus (HEV) is a zoonotic virus that is capable of causing cross-species infection. Rabbits can be experimentally infected with human- and swine-derived HEV-4 in the species Orthohepevirus A, and avian-derived HEV-3 in the species Orthohepevirus B suggesting rabbits can serve as an animal model for zoonotic HEV infection study. However, these studies show that the infectivity of swine HEV isolates in rabbits is not consistent. In this study, the animal study was conducted by the experimental infection of rabbit with a swine-derived HEV-4 isolated in China (designated CHN-SD-sHEV) for 28 weeks post-inoculation (wpi) in compassion to that infected with a rabbit-derived HEV-3 (designated HEV-SX-rHEV). Two rabbits were euthanized every 2 wpi for pathological examinations. The results showed that rabbits infected with CHN-SD-sHEV had the viremia and virus fecal shedding from 1 wpi to 22 wpi and seroconverted from 10 to 28 wpi. Meanwhile, elevated ALT levels were detected at 2 wpi. Moreover, virus replication was confirmed by the detection of both positive- and negative-strand HEV RNAs in the livers and spleens. Diarrhea and hepatocellular lesions were also observed in some animals. In contrast, rabbits experimentally infected with CHN-SX-rHEV exhibited earlier seroconversion, viremia and virus fecal shedding and hepatocellular lesions. Taken together, our data demonstrate that in comparison to the previously reported cases, the swine-derived HEV-4 isolated in China could cross-species infect rabbit accompanied with prolonged virus fecal shedding and liver lesions.

Soil hydraulic conductivity near saturation () is affected by various soil properties operating at different spatial scales. Using noise-assisted multivariate empirical mode decomposition (NA-MEMD), our objective was to inspect the scale-dependent interactions between and various soil properties and to estimate based on such relationships. In a rectangular field evenly across cropland and grassland, a total of 44 sampling points separated by 5 m were selected and measured for at soil water pressure heads of −1, −5 and −10 cm. At each point, the saturated conductivity was estimated using Gardner’s exponential function, and six soil structural and textural properties were investigated. Decomposed into four intrinsic mode functions (IMFs) and a residue by NA-MEMD, each was found to significantly correlate with all six properties at one spatial scale at least. The variations in were primarily regulated by soil structure, especially at the relatively small scales. Multiple linear regression (MLR) failed to regress either IMF1 or IMF2 of each from the soil properties of the equivalent scales and only accounted for 13.7 to 43.6% of the total variance in calibration for the remaining half of the IMF1s and IMF2s. An artificial neural network was then adopted to estimate IMF1 and IMF2, and the corresponding results were added to the MLR estimates at other scales for which each was estimated at the measurement scale. This prediction greatly outperformed the MLR modeling before NA-MEMD and, on average, accounted for additional 74.4 and 73.4% of the total variance in calibration and validation, respectively. These findings suggest nonlinear correlations between and the soil properties investigated at the small scales and hold important implications for future estimations of and as well as other hydraulic properties.

Knowledge of spatial structures of the radionuclides 137Cs and unsupported 210Pb (210Pbex) is vital for developing sound sampling designs that are crucial for deriving quantitative soil erosion estimates. The objectives are to characterize spatial structures of 137Cs and 210Pbex inventories at small spatial scales under different land uses, and to quantify the effects of core sizes on (1) estimated sample means and variances of the 137Cs and 210Pbex inventories and (2) sample numbers required for estimating the mean inventories at a given confidence level. Three different core sizes were used to take soil samples along three 10-m transects at 0.25-m or 0.5-m intervals for each land use. Land uses included cropland, grassland, forestland, and rangeland. 330 samples were analyzed for 137Cs and 210Pbex inventories. Semivariograms were obtained by plotting empirical semivariances with sample separation distances. The spatial correlation distances ranged from 0.2 to 0.75 m for most cases. The semivariances at the separation distances of >0.75 m were close to the variances of the fields for all four land uses, indicating that the spatial distributions of 137Cs and 210Pbex were nearly stationary and had little spatial dependence at scales between 0.75 and 5 m. The overall results suggested that samples taken at a separation distance of >0.75 m would be largely independent and could be composited to form a representative sample for the sampling location for most cases. Given the large spatial variability at such a small scale, quantitative soil erosion rates cannot be estimated for a single soil core, because remarkably different soil erosion rates can be estimated for soil cores taken within a meter. Core size variation between 38 mm and 86 mm has no apparent effect on estimating sample means and sample standard deviations of 137Cs and 210Pbex inventories, except for gravely soils. In general, 15–30 samples are needed to estimate 137Cs reference inventory on reference sites, but may be more for gravely soils. More samples are required for forest and cultivated sites than for uncultivated grassland sites. On measuring sites, it is strongly recommended that 5–15 samples be taken for a grid point and measured individually if feasible or as a combined sample to allow reliable estimation of the mean 137Cs inventory for the location for most soils and land uses. If samples are taken for each of uniformly eroded land form units, the same number of individual samples as on the reference site are recommended. This work will be useful to improving sampling designs and consequently the accuracy of soil erosion estimation of the 137Cs technique.