Optical remote sensing images can be used to monitor slope deformation in mountain regions. Abundant optical sensors onboard various platforms were designed to provide increasingly high ...spatial–temporal resolution images at low cost; however, finding the best image pairs to derive slope deformation remains difficult. By selecting a location in the east Tibetan Plateau, this work used the co-registration of optically sensed images and correlation (COSI-Corr) method to analyze 402 Sentinel-2 images from August 2015 to February 2020, to quantify temporal patterns of uncertainty in deriving slope deformation. By excluding 66% of the Sentinel-2 images that were contaminated by unfavorable weather, uncertainties were found to fluctuate annually, with the least uncertainty achieved in image pairs of similar dates in different years. Six image pairs with the least uncertainties were selected to derive ground displacement for a moving slope in the study area. Cross-checks among these image pairs showed consistent results, with uncertainties less than 1/10 pixels in length. The findings from this work could help in the selection of the best image pairs to derive reliable slope displacement from large numbers of optical images.
Accurate estimation of extreme precipitation is vital for the prediction of hydrologic extremes and flood risk management. Recent satellite-based precipitation products provide important alternative ...sources of data for such applications, yet their quality and applicability with respect to extreme precipitation have not been studied sufficiently. In this study, the performances of the Tropical Rainfall Measuring Mission (TRMM) 3B42 and Global Precipitation Measurement Integrated Multi-satellitE Retrievals (GPM IMERG) data in extreme precipitation estimation were evaluated over China. Both annual maximum precipitation and extreme rainfall events exceeding the 90th percentile were examined and compared with gauge measurements for the periods of 2000–2017 and 2014–2017. It was found that: (1) both satellite products captured the spatial pattern of extreme precipitation well over China with an overall underestimation for extreme rainfall rate and an overestimation for annual total extreme precipitation volume; (2) TRMM 3B42 data had limited ability to detect extreme rainfall events, while GPM IMERG performed slightly better; (3) both products produced good estimation of extreme precipitation with short-medium recurrence intervals, but exhibited consistent underestimation at all return periods; (4) GPM IMERG outperformed TRMM 3B42 for nearly all evaluation metrics when compared over the same time period; (5) the performances were better in south and east China with humid monsoon climate, than in arid west China with high altitude, indicating a significant influence of topography and climate. Our results indicated high potential of satellite products to represent the spatial pattern, overall volume and probability characteristics of extreme precipitation over China, and revealed the general superiority of GPM IMERG to TRMM 3B42. Meanwhile, more studies are still needed to validate data in regions with complex topography and dry climate, and further improve the retrieval algorithm to better support disaster risk reduction and other hydrological applications, especially in areas with a sparse gauge network.
•Spatial pattern and overall volume of extreme precipitation were well captured.•Both TRMM and GPM had limited capability to detect extreme rainfall event.•Good estimation of extreme precipitation of short-medium return period was produced.•GPM outperformed TRMM in extreme precipitation estimation and detection.•The performances were better in humid south and east China than in arid west China.
•Major earthquake trigger thousands of landslides and disturb vast area of vegetation.•How long will mountain environment become stable after major quake is unknown.•Vegetation dynamic indicates the ...stability of post-seismic mountain environment.•The Wenchuan earthquake's impact may disappear within two decades.
Major mountain earthquakes could have long-term impacts on post-seismic landslide activities. Yet, we have limited understanding of the duration of these impacts due to a lack of long-term consistent observation. This study combines multi-year high spatial resolution and high temporal resolution remote sensing images collected before and after the 12 May 2008 MW 7.9 Wenchuan earthquake to investigate post-seismic landslide changes and vegetation recovery processes at landslide sites in the epicentral area. We found that the earthquake caused significant vegetation damage by triggering co-seismic landslides. Since that time, vegetation at these landslide sites has been continuously recovering, and the total post-seismic landslide area is decreasing concurrently. Post-seismic vegetation recovery reflects and possibly promotes the decrease of post-seismic landslide activities. Our findings on post-seismic vegetation recovery at landslide sites indicate that the Wenchuan earthquake's impact on regional post-seismic landslide frequency may disappear within two decades after the major event.
Massive landslides over large regions can be triggered by heavy rainfalls or major seismic events. Mapping regional landslides quickly is important for disaster mitigation. In recent years, deep ...learning methods have been successfully applied in many fields, including landslide automatic identification. In this work, we proposed a deep learning approach, the ResU-Net, to map regional landslides automatically. This method and a baseline model (U-Net) were collectively tested in Tianshui city, Gansu province, where a heavy rainfall triggered more than 10,000 landslides in July 2013. All models were performed on a 3-band (near infrared, red, and green) GeoEye-1 image with a spatial resolution of 0.5 m. At such a fine spatial resolution, the study area is spatially heterogeneous. The tested study area is 128 km2, 80% of which was used to train models and the remaining 20% was used to validate accuracy of the models. This proposed ResU-Net achieved higher accuracy than the baseline U-Net model in this mountain region, where F1 improved by 0.09. Compared with the U-Net model, this proposed model (ResU-Net) performs better in discriminating landslides from bare floodplains along river valleys and unplanted terraces. By incorporating environmental information, this ResU-Net may also be applied to other landslide mapping, such as landslide susceptibility and hazard assessment.
Geological hazards in Xinxian County, Xinyang City, Henan Province, are characterized by their small scale, wide distribution, and significant influence from regional tectonics. This study focuses on ...collapses and landslide hazards within the area, selecting twelve evaluation factors: aspect, slope shape, normalized difference vegetation index (NDVI), topographic relief, distance from geological structure, slope, distance from roads, land use cover type, area of land change (2012-2022), average annual rainfall (2012-2022), and river network density. Utilizing data from historical disaster sites across the region, the information quantity method and hierarchical analysis method are employed to ascertain the information quantity and weight of each factor. Subsequently, a random forest model is applied to perform susceptibility zoning of geological hazards in Xinxian County and to examine the characteristics of these geological disasters. The results show that in the study area, the primary factors influencing the development of geohazards are the distance from roads, rock groups, and distance from geological structure areas. A comparison of the susceptibility results obtained through two methods, the analytic hierarchy process information quantity method and the random forests model, reveals that the former exhibits a higher accuracy. This model categorizes the geohazard susceptibility in the study area into four levels: low, medium, high, and very high. Notably, the areas of very high and high susceptibility together cover 559.17 km
, constituting 35.99% of the study area's total area, and encompass 57 disaster sites, which represent 72.15% of all disaster sites. Geological hazards in Xinxian County frequently manifest on steep canyon inclines, along the curved and concave banks of mountain rivers, within watershed regions, on gully inclines, atop steep cliffs, and on artificially created slopes, among other sites. Areas with very high and high vulnerability to these hazards are mainly concentrated near the county's geological formations. The gneiss formations are widely exposed in Xinxian County, and the gneisses' strength is significantly changed under weathering, which makes the properties of the different degrees of weathering of the rock and soil bodies play a decisive role in the stability of the slopes. This paper provides a basis for evaluating and preventing geologic hazards in the Dabie mountainous area of the South Henan Province, and the spatial planning of the national territory.
Programmed cell death ligand 1 (PD-L1) is a potential predictive biomarker of the response to anti-PD-L1/anti- programmed cell death 1 (PD-1) therapy in multiple cancers, including triple negative ...breast cancer(TNBC). The purpose of this study was to investigate whether PD-L1 expression is homogenous in primary tumors(PTs) and synchronous axillary lymph node metastases(LNMs) of TNBC.
PD-L1 expression was immunohistochemically evaluated in 101 TNBC patients' PTs and paired LNMs. PD-L1 expression in tumor cells and infiltrating immune cells or node lymphocytes in the PTs and associated LNMs was scored separately and was correlated with patients' clinical parameters and prognoses.
PD-L1 expression exhibited spatial heterogeneity in both the tumor cells and the infiltrating immune cells or node lymphocytes of PTs and LNMs. The PD-L1 expression levels were significantly higher in the lymphocytes and tumor cells of the LNMs than in the PTs. PD-L1 expression was also more frequent among the LNMs. PD-L1 expression was associated with high grade and more stromal tumor-infiltrating lymphocytes(TILs). Furthermore, the disease-free survival and overall survival were similar between the PT- negative/LNM- positive and PT- positive/LNM- positive patients, both of which exhibited worse disease-free survival(DFS) thanPT -negative/LNM -negative patients.
The differential expression of PD-L1 between the PTs and LNMs suggests that LNMs PD-L1 status may be used to indicate whether PD-1/PD-L1-targeted therapy would be suitable for a node-positive TNBC patient in the future.
An important form of land degradation is that induced by landslides. Vegetation recovery at coseismic landslide sites not only plays an important role in reducing soil erosion and increasing land ...stability but also records the transformation of loose, exposed landslide surfaces into stable hillslopes during the post‐seismic years. However, little is known about the vegetation recovery process or its influencing factors. In this study, we use the Moderate Resolution Imaging Spectroradiometer (MODIS) normalized difference vegetation index (NDVI) dataset, Tropical Rainfall Measuring Mission (TRMM) 3B42 daily precipitation data, and a digital elevation model (DEM) to study the impacts of precipitation and topographic parameters on vegetation recovery after the 2008 Wenchuan earthquake. Our results reveal significant NDVI decreases during the 2008 earthquake and strong recovery in the following years at the coseismic landslide sites. We also found significant negative correlations between precipitation and derivative of the NDVI trend (NDVIDT) in 2010 and 2011 and significant positive correlations in 2009 and 2013 at the regional scale. These significant negative correlations indicate that precipitation may trigger landslides to remobilize, depressing the recovery of vegetation at coseismic landslide sites during the first few years following a major earthquake. The results further show that site‐specific vegetation recovery is determined by topographic parameters at the local scale. In general, vegetation recovery is weaker at low elevations (<1,300 m) and high elevations (>3,300 m), and it is also weaker on gentler slopes (<35°) than on steeper slopes (>35°).
Debris flows in the Wenchuan seismic region have caused human casualties and severe damage to local infrastructure. Consequently, the triggering rainfall threshold and erosion capability of ...post-quake debris flows has become an important research topic worldwide. In this study, we analyze five years of rainstorms and debris flow data from four typical earthquake-hit regions in order to examine the local rainfall intensity–duration (I-D) thresholds and debris supply conditions. It was found that debris flow events in the four seismic areas exhibited different I-D thresholds, related to local mean annual hourly precipitation and debris flow supply conditions. The I-D thresholds, normalized by mean annual maximum hourly rainfall, illustrate that post-quake rainfall thresholds were reduced by at least 30% compared to pre-quake levels. Regression analysis revealed a clear linear relationship between the debris supply condition and the empirical coefficient, α, of the I-D equation. This means that rainfall thresholds of post-quake debris flows in different areas are distinctive and are strongly affected by sediment volume. Different relationships between the entrainment rate and the debris volume per watershed area and its product with the channel gradient illustrate that stream sediments in Yingxiu and Dujiangyan are more eroded, and that local debris flows might persist over a shorter time than in Qingping and Beichuan in the future. Finally, debris flows in the studied area exhibit no tendency of reduction in erosion competence entrainment rate, as found in Taiwan, which might be indicative of a higher entrainment rate persisting for a longer time.
•The post-quake rainfall thresholds were reduced by at least 30% in comparison with pre-quake levels.•A good linear relation between the debris supply condition and the empirical coefficient α of the I-D equation.•At present, debris flows in the Wenchuan earthquake-hit zone exhibited no tendency of reduction in erosion competence.
Vehicular Edge Computing (VEC) technology holds great promise, but also poses significant challenges to the limited computing power of in-vehicle devices and the capacity of Roadside Units (RSUs). At ...the same time, the highly mobile nature of vehicles and the frequent changes in the content of requests from vehicles make it critical to offload applications to edge servers and to effectively predict and cache the most popular content, so that the most popular content can be cached in advance in the RSU. And also considering protecting the privacy of vehicle user vehicular users (VUs), traditional data-sharing methods may not be suitable for this work, so we use an asynchronous Federated learning (FL) approach to update the global model in time and at the same time can protect the personal privacy of VUs. Unlike the traditional synchronous FL, asynchronous FL no longer needs to wait for all vehicles to finish training and uploading local models before updating the global model, which avoids the problem of long training time. In this paper, we propose an in-vehicle edge computing caching scheme based on asynchronous federated learning and deep reinforcement learning(AFLR), which prefetches possible popular contents in advance and caches them in the edge nodes or vehicle nodes according to the vehicle's location and moving direction while reducing the latency of the content requests. After extensive experimental comparisons, the AFLR scheme outperforms other benchmark caching schemes.
Major earthquakes in mountain regions have persistent and significant influences on post-seismic landslides but their details have not been well understood. This work uses multi-year high-resolution ...satellite images and terrain parameters, such as elevation, slope, and aspect, to examine the topographic changes of post-seismic landslides. Despite disturbances during rainy months, landslide areas decreased significantly from 2008 to 2013 in all terrain parameters, indicating that landslide activity near the epicentre has been recovering to the pre-seismic level. The emergence of an increasingly active landslide type shows that landslide debris has been moving from hillslopes to valleys, which could impact post-seismic debris flows. The findings of this work provide important information for post-seismic infrastructure re-construction and disaster prevention in future mountain earthquake events.
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