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The accurate estimation of forest aboveground biomass is of great significance for forest management and carbon balance monitoring. Remote sensing instruments have been widely applied in forest parameters inversion with wide coverage and high spatiotemporal resolution. In this paper, the capability of different remote-sensed imagery was investigated, including multispectral images (GaoFen-6, Sentinel-2 and Landsat-8) and various SAR (Synthetic Aperture Radar) data (GaoFen-3, Sentinel-1, ALOS-2), in aboveground forest biomass estimation. In particular, based on the forest inventory data of Hangzhou in China, the Random Forest (RF), Convolutional Neural Network (CNN) and Convolutional Neural Networks Long Short-Term Memory Networks (CNN-LSTM) algorithms were deployed to construct the forest biomass estimation models, respectively. The estimate accuracies were evaluated under the different configurations of images and methods. The results show that for the SAR data, ALOS-2 has a higher biomass estimation accuracy than the GaoFen-3 and Sentinel-1. Moreover, the GaoFen-6 data is slightly worse than Sentinel-2 and Landsat-8 optical data in biomass estimation. In contrast with the single source, integrating multisource data can effectively enhance accuracy, with improvements ranging from 5% to 10%. The CNN-LSTM generally performs better than CNN and RF, regardless of the data used. The combination of CNN-LSTM and multisource data provided the best results in this case and can achieve the maximum R2 value of up to 0.74. It was found that the majority of the biomass values in the study area in 2018 ranged from 60 to 90 Mg/ha, with an average value of 64.20 Mg/ha. [ABSTRACT FROM AUTHOR]

The characteristics of sea ice leads (SILs) in the Weddell Sea are an important basis for understanding the mechanism of the atmosphere–ocean system in the Southern Ocean. In this study, we derived the sea ice surface temperature (IST) of the Weddell Sea from MODIS thermal images and then generated a daily SIL map for 2015 and 2022 by utilizing the iterative threshold method on the optimised MOD35 cloud-masked IST. The results showed that SIL variations in the Weddell Sea presented remarkable seasonal characteristics. The trend of the SIL area exhibited an initial rise followed by a decline from January to December, characterised by lower values in spring and summer and higher values in fall and winter. SILs in the Weddell Sea were predominantly concentrated between 70~78°S and 60~30°W. The coastal spatial distribution density of the SILs exceeded that of offshore regions, peaking near the Antarctic Peninsula and then near Queen Maud Land. The SIL variation was mainly influenced by dynamical factors, and there were strong positive correlations between the wind field, ocean currents, and sea-ice motion. [ABSTRACT FROM AUTHOR]

Arctic sea ice outflow to the Atlantic Ocean is essential to the Arctic sea ice mass budget and the marine environments in the Barents and Greenland seas (BGS). With the extremely positive Arctic Oscillation (AO) in winter (JFM) 2020, the feedback mechanisms of anomalies in Arctic sea ice outflow and their impacts on winter–spring sea ice and other marine environmental conditions in the subsequent months until early summer in the BGS were investigated. The results reveal that the total sea ice area flux (SIAF) through the Fram Strait, the Svalbard–Franz Josef Land passageway, and the Franz Josef Land–Novaya Zemlya passageway in winter and June 2020 was higher than the 1988–2020 climatology. The relatively large total SIAF, which was dominated by that through the Fram Strait (77.6 %), can be significantly related to atmospheric circulation anomalies, especially with the positive phases of the winter AO and the winter–spring relatively high air pressure gradient across the western and eastern Arctic Ocean. Such abnormal winter atmospheric circulation patterns have induced wind speeds anomalies that accelerate sea ice motion (SIM) in the Atlantic sector of Transpolar Drift, subsequently contributing to the variability in the SIAF (R=+0.86 , P<0.001). The abnormally large Arctic sea ice outflow led to increased sea ice area (SIA) and thickness in the BGS, which has been observed since March 2020, especially in May–June. The increased SIA impeded the warming of the sea surface temperature (SST), with a significant negative correlation between April SIA and synchronous SST as well as the lagging SST of 1–3 months based on the historic data from 1982–2020. Therefore, this study suggests that winter–spring Arctic sea ice outflow can be considered a predictor of changes in sea ice and other marine environmental conditions in the BGS in the subsequent months, at least until early summer. The results promote our understanding of the physical connection between the central Arctic Ocean and the BGS. [ABSTRACT FROM AUTHOR]

The efficacies and safety of oblique lateral interbody fusion (OLIF) for degenerative lumbar spondylolisthesis (DLS) remains controversial, and long‐term clinical efficacies in particular need to be explored. This study is designed accordingly, therefore, we searched PubMed, Embase, Scopus, Web of Science, Cochrane Library, ProQuest, OVID, and SinoMed for literature, regardless of publication date or language. Taking 12 months after operation as the shortest limit, the outcome measures were extracted, including visual analog scale (VAS), Oswetry dysfunction index (ODI), Japanese Orthopaedic Association (JOA) score, intervertebral disk height (IDH), foraminal height (FH), lumbar lordosis (LL), segment lordosis (SL), slip ratio, and incidence of surgical complications. Meta‐analysis was performed by RevMan 5.4 and Stata 16.0, and results were expressed with MD and 95% CI, and two‐sided p‐values with p < 0.05 being statistically significant. In total, 17 clinical studies (n = 689 patients) were screened, with an average patient age of 63.4 years. Our study revealed that VAS decreased by 4.55 (low back pain) and 5.46 (leg pain) points, respectively. And ODI score decreased by an average of 33.82% while JOA score increased by an average of 11.56 points. In terms of imaging indicators, mean IDH and FH increased by 4.18 and 4.91 mm, mean LL and SL improved by 9.22° and 2.46°, respectively. Besides, mean slip ratio decreased by 10.45%. The incidence of complications was statistically analyzed in 18 studies, with a rate of 4%–54% and an overall incidence of 19%. To sum up, our study was the first to focus on the long‐term efficacies of OLIF treatment for DLS, and to provide further clinical evidence. However, long‐term follow‐up multicenter randomized controlled trials are still needed for further evaluation. [ABSTRACT FROM AUTHOR]

Submerged spur dikes are widely applied in the channel regulation structures of plain sand-bed rivers such as the lower reaches of the Yangtze River; thus, the issue of local scour protection near regulating structures is especially important for structure design engineering. To further scientific research on the local scour of submerged spur dike heads, we investigated rulers describing the variance of the incoming flow dynamic, scale of the spur dike body, width of river bottom protection, etc., responding to the maximum local scouring depth of a submerged spur dike and the distance between the submerged spur dike and dam axis under the conditions of river bottom protection. According to principles of dimensional analysis, we established computational formulas for the maximum local scouring depth of a submerged spur dike and the distance between the submerged spur dike and dam axis, with consideration of bottom protection works for the remaining soft mattress. These research results not only enrich existing research on the calculation of local scour of channel-regulating structures, but they are also a relevant technical reference for the design of water conservancy and waterway engineering. [ABSTRACT FROM AUTHOR]

Urban forest carbon sequestration represents an important component of the global forest carbon pool; however, accurate measurements are limited by the inability of existing field stand models to match the specificity of urban greening species. Herein, canopy volume, carbon stock, and the biomass expansion factor (BEF) of 30 Koelreuteria paniculate trees were measured based on terrestrial laser scanning (TLS) and compared to the results of existing wood volume and carbon stock model measurements. The findings revealed that (1) TLS point cloud data were highly reproducible and accurate (root mean square error of tree height and diameter at breast height were ±0.35 m and ±0.33 cm, respectively). (2) Owing to human interference and cluttered urban environments, the BEF of urban greening tree species fluctuated irregularly, considerably different from that of natural forest stands. (3) Leaf carbon stocks were influenced by the size of the voxel. (4) Different tree measurement factors maintained variable degrees of influence on BEF (height under branch, volume of thick branch, crown width, and projected areas of tree-crown produced correlation coefficients of −0.64, 0.54, 0.45, and 0.43, respectively). Accordingly, the carbon stock and BEF of urban greening tree species can be accurately calculated via TLS without damage. [ABSTRACT FROM AUTHOR]

Forests are crucial in carbon sequestration and oxygen release. An accurate assessment of forest carbon storage is meaningful for Chinese cities to achieve carbon peak and carbon neutrality. For an accurate estimation of regional-scale forest aboveground carbon density, this study applied a Sentinel-2 multispectral instrument (MSI), Advanced Land Observing Satellite 2 (ALOS-2) L-band, and Sentinel-1 C-band synthetic aperture radar (SAR) to estimate and map the forest carbon density. Considering the forest field-inventory data of eastern China from 2018 as an experimental sample, we explored the potential of the deep-learning algorithms convolutional neural network (CNN) and Keras. The results showed that vegetation indices from Sentinel-2, backscatter and texture characters from ALOS-2, and coherence from Sentinel-1 were principal contributors to the forest carbon-density estimation. Furthermore, the CNN model was found to perform better than traditional models. Results of forest carbon-density estimation validated the improvements effectively by combining the optical and radar data. Compared with traditional regression methods, deep learning has a higher potential for accurately estimating forest carbon density using multisource remote-sensing data. [ABSTRACT FROM AUTHOR]

Large marginal sandbanks in tidal rivers experience periodic splitting processes. In this paper, the morphodynamic evolution of Jingjiang Beach, a sandbank on the Yangtze tidal river, has been investigated based on measured data. The results show that the duration of the splitting process in the middle and lower sections of Jingjiang Beach is 4–6 years. The periodical evolution occurred both in flood season and dry season, with a slight difference in the initial stage of splitting. This paper focuses on the evolution characteristics related to strong human activities since 2003. Ever since the second stage of the 12.5 m Deepwater Channel Project (DCP), the volumes above the 10 m and 12.5 m isobaths of Jingjiang Beach have been generally decreasing. The elevation data in recent years have demonstrated that the upper section, and nearshore side of the middle section, of Jingjiang Beach have tended to be stable. Moreover, the migration distance for a splitting sand body at the tail of Jingjiang Beach appears to have shortened. With the operation of the Three Gorges Reservoir, the number of days with discharge less than 15,000 m3/s has shown a decreasing trend; thus, the development scale of Jingjiang Beach could decline in the future. [ABSTRACT FROM AUTHOR]

Quantification of the spatial variability and long‐term changes of Arctic sea ice motion is important for understanding the mechanisms of rapid Arctic sea ice decline because sea ice motion determines ice mass advection, outflow, thickness redistribution, as well as the formation of leads and ridges associated with ice deformation. The spatiotemporal changes in Arctic sea ice motion between 1979 and 2019 and their responses to atmospheric forcing were analysed using satellite‐derived sea ice motion products and atmospheric reanalysis data. The pan‐Arctic average sea ice drift speed increased significantly for all seasons between 1979 and 2019 (p <.001). Rates of increase were higher in autumn and winter than in spring and summer. Spatially, rates of increase in the peripheral seas in the Pacific sector—the Beaufort, Chukchi and East Siberian Seas—were higher than in the central Arctic Ocean and the peripheral seas in the Atlantic sector—the Kara and Laptev Seas. On the contrary, Arctic wind speed increased significantly only in autumn (p <.01). However, the correlation between wind speed and ice speed was the lowest in this season, suggesting that wind forcing is unable to completely account for drift speed increase. In general, the trends in above‐average drift speeds—retrieved from grid cells with the relatively high drift speeds—were statistically significant and were larger than that in average drift speeds probably because of enhanced response of ice motion to extreme wind forcing. The influence of the Arctic Oscillation, Beaufort High, and North Atlantic Oscillation on the zonal ice speed was symmetrical between the Pacific and Atlantic sectors of the Arctic Ocean, while the influence of the Dipole Anomaly and the east–west surface air pressure gradient in central Arctic on the meridional ice speed was distributed in an annular pattern and was the strongest along the Transpolar Drift Stream. [ABSTRACT FROM AUTHOR]

As a key component of global change, dam‐induced sediment reduction occurs in large rivers worldwide, which has profound implications on the fluvial systems. However, the systematic change of suspended sediment concentration (SSC) and its dynamic processes are not well known. We summarize typical SSC changes and propose a new sediment modeling framework for heavily dammed fluvial systems with the Changjiang (Yangtze River) as a background. We find that the fluvial SSC has declined by an order of magnitude, i.e., from ∼1.0 to ∼0.1 kg/m3, and even to ∼0.01 kg/m3 locally. The SSC distribution pattern along the mainstream has changed remarkably, with the sediment source/sink being partially reversed. Downstream of the Three Gorges Dam, the SSC recovery capacity gradually decreases with the sediment erosion quantity accumulated over time, and the SSC contribution rate of a linked large lake (Dongting) will change from negative (ca. −39%) to positive (ca. 17%), in the coming decades. Plain Language Summary: Suspended sediment plays a key role in fluvial nutrient transport and aquatic ecological processes. Globally river damming has led to sediment discharge reduction to the sea, yet the systematic riverine concentration (SSC) changes and their mechanisms remain poorly understood. Herein, we propose a new modeling framework for reproducing and forecasting suspended sediment processes for dammed fluvial systems with the Changjiang as a reference. Results show a sediment source/sink reverse, downstream recovery capacity decrease and a change in river‐lake relationship under severe SSC decline. These findings offer essential guidelines for river management subject to super reservoirs, which have been built (e.g, the Three Gorges Reservoir) or planned in large rivers, such as the Congo and Amazon River. Key Points: Suspended sediment concentration of the Changjiang River has decreased by an order of magnitude in recent 3 decades from ∼1.0 to ∼0.1 kg/m3Sediment source/sink reverse partially and downstream recovery capacity decrease exponentially under the reservoir operationPredicted by a new sediment modeling framework, the river‐lake relationship in the fluvial system will change considerably in 2030s [ABSTRACT FROM AUTHOR]

A tidal river is a special zone where the basic hydrodynamic process is the interaction between riverine flow and tides. Existing studies focus mainly on the water level fluctuations, while the effort is limited regarding the flow regime between uni- and bi-directional currents. Along a tidal river, the current direction reverses where the landward flow meets with seaward flow. So far, the occurrence and movement of current reversal is not fully investigated, and the number and location of reversal points are not well understood. In this study, the water flow in the Yangtze tidal river was simulated using a hydrodynamic model, and the phenomenon of current reversals in the tidal river were investigated. It is found that in the dry season up to three reversal points may occur simultaneously, including two convergence points and one divergence point, separating the entire tidal river into two seaward-current reaches and two landward-current reaches. These multiple reversal points result from the co-existence of the preceding and present flood tidal waves. During a spring tide the peak landward flux of the preceding wave can reach up to 10,000 m3/s, about the same magnitude as the riverine discharge and the length of the landward-current occupation is as large as 120 km. It was also found that a current reversal point always coexists with a zero-gradient point of water level, and the location of this reversal is downstream of the zero-gradient point. The reversals shift landward from the river mouth consecutively, and could finally disappear farther at the upper reach of the tidal river. The bidirectional flow could extend up to 550 and 200 km upstream from the river mouth in the dry and wet seasons, respectively. The current reversals are influenced by the discharge regulation of the Three Gorges Dam. These movements of current reversals in the flow regime could furtherly have significant impact on local hydrodynamic process and material transportation. Image 1 • Transition between uni- and bi-directional flows in a large tidal river is studied. • Up to three current reversals emerge simultaneously in dry season. • Preceding landward flow occupies as long as 100 km with the max-flux of 10000 m3/s. • A reversal is always located downstream of a zero-gradient-water-level point. • Movement of reversals is multi-timescale due to tides and river flow. [ABSTRACT FROM AUTHOR]

Estuaries are transition regions between marines and inland rivers where hydrodynamic processes are controlled by oceanic tidal waves and fluvial discharges. Moreover, human activities, such as the growing number of water conservancy projects, have an increasing impact on estuarine hydrodynamics. However, these natural variations and anthropogenic impacts are not yet fully understood, especially for large estuaries. In this study, the interactions between tidal waves and riverine flows in the Yangtze Estuary were investigated using the methods of numerical modelling and harmonic analysis. The focus of this study is on the characteristics of tides in the coastal area, seasonal variations in hydrodynamic process and impacts of reservoir regulation on tidal constituents in the tidal river. The results indicate that in the coastal area, semi-diurnal and diurnal tidal constituents propagate in different directions along the coast and that the tidal waves in the coastal area are stationary, i.e. the amplitude and phase do not change in time. However, in the tidal river, significant seasonal variations in the water surface slope, water level fluctuations and damping process can be identified. In the dry season, the tidal signal can reach Datong station, >600 km from the estuary mouth, whereas in the wet season, the signal's reach is approximately 350 km. From the dry to wet seasons, the maximum decrease in the amplitude of the dominant M 2 tide is approximately 0.3 m. The amplitudes of the tidal constituents do not decrease monotonically because of the complex interactions among the bed friction, river discharge and channel width convergence as well as energy transmission between the tidal constituents. Because the Three Gorges Reservoir is used to regulate seasonal discharge, the increase in the accumulated amplitudes of the six major tides can reach up to 0.1 m in the tidal river reach. [ABSTRACT FROM AUTHOR]

Focuses on a study which details the physiologic influences of homocysteine to cerebrovascular diseases. Methodology of the study; Physiologic action of homocysteine; Discussion on the results of the study.

Determines whether nitric oxide (NO) produced by an isoform of NO synthase (iNOS) contributed to ischemic brain damage. Effect of aminoguanidine or arginine on infarct volume and cerebral constitutive isoforms of NOS activity; Effect of aminoguanidine on NOS activity in the area of infarction; Cerebrospinal effects of aminoguanidine.