Search

Landslide-induced surges, as a complex type of fluid-solid coupling problem, are widespread in mountain regions and cause disastrous consequences. In order to reproduce the entire process of landslide-induced surge, by taking full advantage of material point method (MPM) in simulating large deformation of soil and gravity-driven flow of water, the two-phase double-point material point method (TPDP-MPM) was extended: a new algorithm handling the boundary without setting boundary particles was proposed. The classical submarine block-induced surge test and sand column collapse experiment were numerically simulated by the MPM and verified the effectiveness of the program. After that, the multiphase coupling process of Lituya Bay landslide-induced surge was simulated and verified the reliability of the TPDP-MPM code, which have achieved parallel computing by making use of OpenMP model. By comparing the results of numerical simulation with the model experiment, the two-phase double-point material point method can well simulate the starting, propagation, run-up and reflux stage of landslide-induced surge. Moreover, the extension mechanism of landslide-surge disaster chain in both time and space is revealed from the perspective of energy. This study provides a reliable tool for the analysis and assessment of landslide-induced surge disasters.

The Eastern Route of the South-to-North Water Diversion Project (SNWDP-ER) is a large scale multi-decade infrastructure project aiming to divert substantial amounts of water (≈45 billion m3 yr−1) to alleviate water shortage in comparatively arid regions of northern China. The project has ramifications for hydrological connectivity and biogeochemical cycling of dissolved organic matter (DOM) in regional lakes affected by the project. We carried out an extensive field sampling campaign along the SNWDP-ER in different hydrological seasons of 2018 and monthly observations in Lake Hongze and Lake Luoma from April 2018 to June 2021. We found the lakes connecting to the SNWDP-ER had higher mean DOC, specific UV absorbance, higher ratio of humic-like to protein-like fluorophores (Humic : Protein), and shallower spectral slope (S275–295) in the wet season compared to the wet-to-dry transition, and dry seasons. The southern lakes and Yangtze River had lower DOC concentration, bioavailable DOC (BDOC), and higher DOM aromaticity compared to the northern two downstream lakes. Ultrahigh-resolution mass spectrometry (FT-ICR MS) revealed higher relative abundance of CHO-containing and aromatic compounds in the Yangtze River and the southern three upstream lakes compared to the northern two lakes. The data from Lake Hongze and Lake Luoma, studied in different hydrological seasons, suggest that water delivery had high consistency in DOM composition and BDOC over the season. We conclude that positioning along the watercourse and seasonally variable hydrological conditions play an important role in influencing the DOM composition and bioavailability of key lakes connecting to the SNWDP-ER. Our results indicated that the water diversion project delivers water with low DOC concentration and higher aromaticity and thus is of higher quality since it has higher DOM removal potential during drinking water treatment.

Long-term decreases in the incident total radiation and water clarity might substantially affect the underwater light environment in aquatic ecosystems. However, the underlying mechanism and relative contributions of radiation dimming and decreasing water clarity to the underwater light environment on a national or global scale remains largely unknown. Here, we present a comprehensive dataset of unprecedented scale in China’s lakes to address the combined effects of radiation dimming and decreasing water clarity on underwater darkening. Long-term total radiation and sunshine duration showed 5.8% and 7.9% decreases, respectively, after 2000 compared to 1961–1970, resulting in net radiation dimming. An in situ Secchi disk depth (SDD) dataset in 170 lakes showed that the mean SDD significantly decreased from 1.80 ± 2.19 m before 1995 to 1.28 ± 1.82 m after 2005. SDD remote sensing estimations for 641 lakes with areas ≥ 10 km2 showed that SDD markedly decreased from 1.26 ± 0.62 m during 1985–1990 to 1.14 ± 0.66 m during 2005–2010. Radiation dimming and decreasing water clarity jointly caused an approximately 10% decrease in the average available photosynthetically active radiation (PAR) in the euphotic layer. Our results revealed a more important role of decreasing water clarity in underwater darkening than radiation dimming. A meta-analysis of long-term SDD observation data from 61 various waters further elucidated a global extensive underwater darkening. Underwater darkening implies a decrease in water quality for potable water supplies, recession in macrophytes and benthic algae, and decreases in benthic primary production, fishery production, and biodiversity.

Many factors have been reported to affect material cycling in lakes, but the combined and cascading impacts of external environmental factors and in-lake biota on lake carbon cycling are poorly understood. We elucidated the influencing pathways of geoclimatic factors, lake morphometry, land-use type, chemical and physical factors, and biological taxa (phytoplankton and macroinvertebrates) on the concentrations of two important components of carbon cycling, i.e., dissolved organic matter (DOM) and methane (CH

Elucidation of the linkages between the bacterial community composition and chromophoric dissolved organic matter (CDOM) in lake ecosystems is critical for the understanding of the inland water carbon cycling. Despite substantial research into the relationship between the bacteria community and the bulk DOM pool, knowledge of the specific relationship between the optical dynamics of DOM and the bacterioplankton community in lake ecosystems is still poor. We investigated the linkages between the optical dynamics of DOM and bacteria composition in shallow eutrophic Lake Taihu, China. Redundancy Analysis (RDA) indicated that besides water temperature and phytoplankton biomass, also CDOM was an important factor determining the composition of the bacterial community. Generalized Additive Models (GAM) showed that terrestrial humic-like C1 and tyrosine-like C4 were the key factors explaining the abundance of the main bacterial clades. C1 was closely correlated with Verrucomicrobia, Actinobacteria, Alphaproteobacteria, Betaproteobacteria and Planctomycetes, and C4 was closely related to the latter two and to Bacteroidetes. At family level, the dominant families – Pelagibacteraceae (Alphaproteobacteria) and Gemmataceae (Planctomycetes) – were related to both allochthonous and autochthonous CDOM fluorophores but responded differently to the various CDOM components. Tryptophan-like C2 was significantly and positively correlated with Gemmataceae and Ellin6075 (Acidobacteria). Additionally, we found that the biomasses of Cyanophyta, terrestrial humic-like C1, tryptophan-like C4 and C5 were significantly related to the richness of heterotrophic bacterioplankton. Our results provide new insight into the relationship between bacteria and DOM optical dynamics although the mechanisms leading to these relationships need further experimental investigations.

Porous carbon composite electrodes have attracted extensive attention due to their excellent electrochemical performance toward energy storage applications. In this work, hierarchical nitrogen-containing porous carbon (HNPC) and α-MnO2 nanowires composite electrode is prepared through a template method. The as-prepared composite electrode, characterized as one-dimensional nanowires inserted into three-dimensional interconnected porous structures, exhibits high specific capacitance of 204.6 F g−1 at 1 A g−1 and excellent cycling stability (97.2% remains after 5000 cycles). Moreover, the fabricated asymmetric supercapacitor based on HNPC//HNPC/MnO2 achieves a wide working voltage window of 1.8 V and a high energy density up to 30.1 Wh kg−1 at a power density of 900.0 W kg−1. The results indicate that the HNPC/MnO2 composite electrodes with excellent electrochemical performance have promising perspective in supercapacitor applications.

The impoundment of the Three Gorges Reservoir (TGR), the largest hydropower project in the world, has altered the sediment deposition and erosion regime of downstream-linked rivers and lakes. The extent to which the TGR impoundment has changed the surface areas of the two largest freshwater lakes in China, Lake Dongting and Lake Poyang, remains largely unknown. Here, we compared the surface areas of the two lakes pre and post the TGR impoundment as well as with a modelled non-TGR scenario. We found that the mean surface areas of Lake Dongting and Lake Poyang during the post-TGR period (2003–2016) were significantly smaller than in the pre-TGR period (1956–2002) and in the modelled non-TGR scenario (2003–2016). The impoundment of TGR has led to a shift from a sediment deposition regime to an erosion-dominated regime of the downstream-linked rivers and the two lakes. The impoundment of TGR further changed the seasonal variabilities in discharge and water level in the downstream-linked rivers and the two lakes, especially in the flood season. Our results suggest that TGR resulted in a 5.1%, 16.2%, and 12.2% decrease of the surface area of Lake Dongting in June 2003–September 2006, October 2006–September 2008, and October 2008–December 2016, respectively, and a corresponding decrease of 12.4%, 19.6%, and 15.8% for Lake Poyang. These changes cannot be attributed to variations in rainfall as no significant differences were found in the annual or monthly mean rainfall in the watersheds upstream of Luoshan and Jiujiang + Hukou between the pre-TGR and the post-TGR period. Our results call for the development of a strong holistic management plan for cascading reservoirs, including TGR, to minimize the damage of downstream lake ecosystems.

Cyanobacterial blooms are increasing in magnitude, frequency, and duration worldwide. However, our knowledge of cyanobacterial blooms dynamics and driving mechanisms is still limited due to their high spatiotemporal variability. To determine the potential driving mechanisms of cyanobacterial blooms in oligotrophic lakes, we collected a high-frequency depth profile of chlorophyll fluorescence (ChlF) and synchronous water quality, hydrometeorological data in early spring 2016 in oligotrophic Lake Qiandaohu. The vertical distribution of ChlF exhibited two patterns, "aggregated" and "discrete", using Morisita's index, and the aggregated ChlF presented subsurface chlorophyll maxima during the thermal stratification period. The ChlF concentration was positively correlated with water temperature and negatively correlated with turbidity. Significantly linear relationships were observed between ChlF vertical structure parameters (e.g., Morisita's index, subsurface chlorophyll maxima depth and thickness) and thermal stratification parameters (e.g., mixing layer depth and relative water column stability). After rainstorm floods, the ChlF pattern suddenly change from "aggregated" to "discrete" and a ChlF concentration1 μg/L was observed for 7-11 days with a significant increase in the mixing depth layer and turbidity. The results suggest that cyanobacterial blooms are robustly associated with thermal stratification and rainstorm floods in the deep and oligotrophic lake. Thermal stratification boosts surface phytoplankton accumulation by increasing water temperature, enhancing light availability and restricting phytoplankton vertical distribution. Rainstorm floods interrupt the accumulation by disrupting thermal stratification and decreasing the available light. Furthermore, wind speed and air temperature both regulate the phytoplankton dynamics by affecting thermal stratification. Our research quantifies the cyanobacterial bloom dynamics and their relationship between environmental factors, improving our knowledge of the driving mechanisms of cyanobacterial bloom for the protection of drinking water safety and aquatic organism health in lakes.

Nutrient enrichment is a major cause of water eutrophication, and variations in nutrient enrichment are influenced by environmental changes and anthropogenic activities. Accurately estimating nutrient concentrations and understanding their relationships with environmental factors are vital to develop nutrient management strategies to mitigate eutrophication. Landsat 8 Operational Land Imager (OLI) data is used to estimate nutrient concentrations and analyze their responses to hydrological and meteorological conditions. Two well-accepted empirical models are developed and validated to estimate the total nitrogen (TN) and total phosphorus (TP) concentrations (CTN and CTP) in the Xin'anjiang Reservoir using Landsat 8 OLI data from 2013 to 2016. Spatially, CTN decreased from the transition zone to the riverine zone and the lacustrine zone. On the other hand, CTP decreased from the riverine zone to the transition zone and the lacustrine zone. Temporally, CTN displayed elevated values during the late fall and winter and had lower values during the summer and early fall, whereas CTP was higher during the spring and lower during the winter. Among the environmental factors, the rainfall and the inflow rate have strong positive correlations with the nutrient concentrations. TN is more sensitive to meteorological factors (wind speed, temperature, sunshine duration), and the spatial driving forces vary among the different sections of the reservoir. However, TP is more easily influenced by human activities, such as fishery and agricultural activities. Current results would improve our understanding of the drivers of nutrients spatiotemporal variability and the approach in this study can be applicable to other similar reservoir to develop related strategies to mitigate eutrophication.

Quantitative global assessments of aquatic vegetation dynamics in lakes are lacking despite reports of the losses of submerged aquatic vegetation. We conducted a comprehensive global assessment of aquatic vegetation at 155 study sites. We also included ≥ 2 yr of information on the absolute or relative area of aquatic vegetation from the literature. We calculated the difference between initial and final observed aquatic vegetation area (or cover) to represent the overall trends over time. We classified the study sites of aquatic vegetation into the categories “increasing”, “decreasing” or “no change” using a threshold of 10%. Aquatic vegetation area (or cover) decreased in 101 study sites, particularly in China (35 study sites), increased in 43 study sites, and showed no marked changes in 11 study sites. Our results revealed an accelerating decrease rate (vegetation loss in terms of area or cover) over time: 13.5 ± 16.9%/yr (1900–1980), 21.8 ± 28.9%/yr (1980–2000) and 33.6 ± 59.8%/yr (after 2000). Moreover, the area (or cover) increase rate in lakes where aquatic vegetation showed recovery decreased from 23.5 ± 29.9%/yr (1980–2000) to 16.8 ± 13.2%/yr (after 2000). We conclude that aquatic vegetation loss is accelerating, especially that of submerged aquatic vegetation and particularly in lakes with an area larger than 50 km 2 . The predominance of decreasing vegetation found in our study is likely caused by multiple stressors such as eutrophication, algal blooms, land reclamation, aquaculture cultivation and global climate changes.

Multicolor luminescent carbon dots (Cdots) are of immense importance nowadays, while it still a challenge to construction of full-color light-emitting Cdots and their efficient solid-state materials. Here in, we fabricated a facile method to synthesize multicolor Cdots by adjustment of the reaction temperature. Although all samples showed uniform distribution of particles size and similar graphite structure, the surface chemical composition gradually varied among Cdots, especially the oxygen contents and nitrogen contents. Detailed material characterization has revealed that this tunable emission is results from the changes of the chemical composition. It is believed that the surface oxidation become more severe at high temperature, resulting in the formation of higher oxygen and nitrogen, which are responsible for the long-wavelength emission. Meanwhile, flexible solid-state materials were successfully created by combination of organosilane (OSi) and Cdots, which can be used to prevent the aggregation-induced solid-state fluorescence quenching. Finally, red Cdots/OSi was stacked on the Y 3 Al 5 O 12 :Ce 3+ (Ce 3+ : YAG) phosphor-in-glass (Ce-PiG) via tape-casting technology. Then, warm white light-emitting diodes (WLEDs) were constructed by these materials and GaN chips. As the Cdots increases, the correlated color temperature (CCT) decreases while the color rendering index (CRI) increases, and the color coordinates shift towards the red region. The resulting color converting material produced a warm white by adjusting red Cdots content, which will be a promising candidate for applications in the warm WLED.

Perturbations of rainwater chromophoric dissolved organic matter (CDOM) fluorescence induced by changes in rainfall intensity and pH were investigated by field observations and laboratory pH titrations. Microbial humic-like fluorophores dominated the rainwater CDOM pool, followed by tryptophan-like and tyrosine-like substances. Increased rainfall intensity had notable dilution effects on all six fluorescent components (C1-C6) identified using parallel factor (PARAFAC) analysis, the effect being especially pronounced for the microbial humic-like C1, tryptophan-like C3, and tyrosine-like C5. The results also indicated that increasing pH from 7 to 9 led to decreased fluorescence intensity (Fmax) of all the six components, while a pH increase from 5 to 7, resulted in increasing Fmax of terrestrial humic-like C2, tyrosine-like C5, and tryptophan-like C6 and decreasing microbial humic-like C1, tryptophan-like C3, and fulvic-like C4. Two-dimensional correlation spectroscopy (2D-COS) demonstrated that synchronous fluorescence responded first to pH modifications at fulvic-like wavelength (λEx/λEm = ∼316/416 nm), followed by tyrosine-like wavelength (λEx/λEm = ∼204/304 nm), tryptophan-like wavelength (λEx/λEm = ∼226/326 nm), microbial humic-like wavelength (∼295/395 nm), and finally terrestrial humic-like wavelength (∼360/460 nm). Our results suggest that a decrease in areas affected by acid rain in South China occurring at present may possibly result in apparent compositional changes of CDOM fluorescence. The decreased rainfall in South-West China and increased rainfall in North-West China during the past five decades may possibly accordingly result in increased and decreased Fmax of all the six components identified in South-West and North-West China, respectively.

Ag nanoparticles (NPs) show a excellent surface plasmon resonance (SPR), which is expected to enable fluorescence enhancement. In this study, a facile approach is proposed for fabrication of Ag NPs/long-wavelength carbon dots (Ag-LCDs) hybrids, wherein Ag NPs work as a fluorescent reinforcer to enhance photoluminescence (PL) intensity of LCDs. The largest enhancement was acquired through adjusting the volume ration between Ag NPs and LCDs. In this process, PL decay is considered as an important and simple characterization to speculate the metal enhanced fluorescence (MEF) mechanism. On the basis of result of small reduction in lifetime, we proposed that the mechanism may be predominantly derived from the localized effectric field effect and partly from the intrinsic radiative decay rate. Moreover, spin-coating technology was utilized to produce LCDs and Ag-LCDs hybrids films. Then, white light-emitting diodes (white LEDs) were constructed by these films with controllable thicknesses and GaN chips. The constructed white LED presented excellent optical performances with an optimal color coordinates (CIE) of (0.33, 0.35), a color rendering index (CRI) of 74.6, a correlated color temperature (CCT) of 5435 K. Notably, the existence of Ag NPs enable these LCDs to improve the luminous efficacy (LE) from 32.63 lm W−1 to 41.26 lm W−1. Such superior optical merits enable them the promising potentials for application in optical devices.

The present study demonstrates that the ratio of fluorescence integration of peak C to peak T (IC:IT) can be used as an indicator tracing the compositional dynamics of chromophoric dissolved organic matter (CDOM). CDOM absorption and fluorescence spectroscopy and stable isotope δ13C were determined on a seasonal basis in seventeen Chinese inland waters as well as in a series of mixing and photodegradation experiments in the lab. A strong positive linear correlation was recorded between IC:IT and the ratio of terrestrial humic-like C1 to tryptophan-like C4 (C1:C4) derived by parallel factor analysis. The r2 for the linear fitting between IC:IT and C1:C4 (r2=0.80) was notably higher than between C1:C4 and other indices tested, including the ratio of CDOM absorption at 250nm to 365nm, i.e. a(250):a(365) (r2=0.09), spectral slope (S275-295) (r2=0.26), spectral slope ratio (SR) (r2=0.31), the humification index (HIX) (r2=0.47), the recent autochthonous biological contribution index (BIX) (r2=0.27), and a fluorescence index (FI370) (r2=0.07). IC:IT exhibited larger variability than the remaining six indices and a closer correlation with stable isotope δ13C than that observed for a(250):a(365), S275-295, SR, FI370, and BIX during field campaigns. Confirming our field observations, significant correlations were recorded between IC:IT and the remaining six indices, and IC:IT also demonstrated notably larger variability than the six other indices during our wastewater addition experiment. Compared with HIX, eutrophic water addition and photobleaching substantially decreased IC:IT but had no pronounced effect on a(250):a(365), S275-297, SR, FI370, and BIX, further suggesting that IC:IT is the most efficient indicator of the CDOM compositional dynamics.

Light determines macrophyte distribution, community composition and biomass in shallow lakes. Therefore, it is vital to determine the critical underwater light climate thresholds for macrophyte degradation and recovery. In this study, we first proposed a novel index, defined as the ratio of euphotic depth (Zeu) to water depth (WD), as a measure of the underwater light supply for macrophytes. The underwater light environment in Lake Taihu (a large, shallow, eutrophic lake) was then characterized based on this index (Zeu/WD) using field measurements collected from 2006 to 2013 (8 years × 4 seasons × 32 sites). The distribution of the macrophyte presence frequency (MPF, the number of investigations that identified macrophytes divided by the total number of investigations) was greater than 0.70 in Xukou Bay and East Lake Taihu over the 32 investigations, followed by the other sites distributed in East Lake Taihu. The proportion of macrophyte coverage increased with the increase in Zeu/WD. A significant relationship was observed between Zeu/WD and MPF for the 19 sites with macrophytes (r2 = 0.48, p

Drinking water lakes are threatened globally and therefore in need of protection. To date, few studies have been carried out to investigate how the composition and dynamics of chromophoric dissolved organic matter (CDOM) in drinking water lakes are influenced by inflow rate. Such CDOM can lead to unpleasant taste and odor of the water and produce undesirable disinfection byproducts during drinking water treatment. We studied the drinking water Lake Qiandao, China, and found that the concentrations of suspended particulate matter (SPM) in the lake increased significantly with inflow rate (p 0.001). Similarly, close relationships between inflow rate and the CDOM absorption coefficient at 350 nm a(350) and with terrestrial humic-like fluorescence C3 and a negative relationship between inflow rate and the first principal component (PC1) scores, which, in turn, were negatively related to the concentrations and relative molecular size of CDOM (p 0.001), i.e. the concentration and molecular size of CDOM entering the lake increased proportionately with inflow rate. Furthermore, stable isotopes (δD and δ(18)O) were depleted in the upstream river mouth relative to downstream remaining lake regions, substantiating that riverine CDOM entering the lake was probably driven by inflow rate. This was further underpinned by remarkably higher mean chlorophyll-a and in situ measured terrestrial CDOM fluorescence (365/480 nm) and apparent oxygen utilization (AOU), and notably lower mean PC1 and CDOM spectral slope (S275-295) recorded in the upstream river mouth than in the downstream main lake area. Strong negative correlations between inflow rate and a(250):a(365), S275-295, and the spectral slope ratio (SR) implied that CDOM input to the lake in rainy period was dominated by larger organic molecules with a more humic-like character. Rainy period, especially rainstorm events, therefore poses a risk to drinking water safety and requires higher removal efficiency of CDOM during drinking water treatment processes.

3-chloropropane-1, 2-diol (3-MCPD) esters are a kind of food processing contaminants that especially occur in edible oil. This study investigated the impact of various factors on the formation of 3-MCPD esters in edible oil models with sodium chloride as chlorine donator during heat processing. The amount of 3-MCPD esters generated in the models were positively correlated with the concentration of sodium chloride. Fe3+ could significantly promote the formation of 3-MCPD esters. The formation of 3-MCPD esters also depended on pH value of oil, heating temperature and time. The highest level of 3-MCPD esters were obtained at pH 4.0 (2925.3 μg/kg), at 220 °C (9509.8 μg/kg) and for 8 h (4852.4 μg/kg), respectively. 3-MCPD esters were generated much more in the continuous heating model than in the intermittent one. The results are valuable to better understand the formation of 3-MCPD esters and also can provide references for reduction of 3-MCPD esters during edible oil processing and household cooking.

Knowledge of stormwater river plume dynamics is important for the management of lake water quality because river discharge associated with rainstorms can be a major source of pollutants for lake waters. Total suspended matter (TSM) derived from the discharge of sediment-laden rivers is highly variable over a wide range of time and space scales. In the present study, the first use of remote sensing to monitor the river TSM plume was conducted to investigate the effects of heavy rainfall events on Lake Taihu by the largest inflowing river (Tiaoxi River) based on a calibrated and validated model using daily 250 m MODIS imagery in band 1 (620–670 nm). From 2004 to 2013, 48 MODIS images of 20 heavy rainfall events were obtained, showing that the area of the TSM plume significantly increased in the waters adjacent to the inflowing river, reflecting runoff input. The TSM concentration of the river plume after heavy rainfall was significantly higher than that before rainfall (ANOVA, p ˂ 0.001). A significantly positive correlation between the TSM plume area and the rainfall amount in heavy rainfall events ( p ˂ 0.01) was also observed. The heaviest rainfall event, in October 2013, caused a river plume with an area of 302.8 km 2 , which lasted for more than 10 days. The significant increase in the frequency and rainfall amount of rainstorms and large rain in the past 50 years (1965–2014) in Lake Taihu under global warming indicated an important role of remote sensing in monitoring the river plume resulting from heavy precipitation. The present study demonstrates that remote sensing tools can be valuable instruments in the detection and tracking of the effect of heavy rainfall events on the distribution and diffusion of the TSM concentration in the lake. The results obtained from the present study are valuable for further hydrological research on the Tiaoxi River, particularly for the immediate assessment of flood impacts on soil erosion of the catchment.

Biological activity in lakes is strongly influenced by hydrodynamic conditions, not least turbulence intensity; which increases the encounter rate between plankter and nutrient patches. To investigate whether enhanced turbulence in shallow and eutrophic lakes may result in elevated biological production of autochthonous chromophoric dissolved organic matter (CDOM), a combination of field campaigns and mesocosm experiments was used. Parallel factor analysis identified seven components: four protein-like, one microbial humic-like and two terrestrial humic-like components. During our field campaigns, elevated production of autochthonous CDOM was recorded in open water with higher wind speed and wave height than in inner bays, implying that elevated turbulence resulted in increased production of autochthonous CDOM. Confirming the field campaign results, in the mesocosm experiment enhanced turbulence resulted in a remarkably higher microbial humic-like C1 and tryptophan-like C3 (p

Field campaigns and an incubation experiment were conducted to evaluate the sources of chromophoric dissolved organic matter (CDOM) in black water spots in highly polluted regions of the Chinese Lake Taihu. A significant positive correlation (p

Light attenuation is considered as a sentinel for environmental change in lakes and has a profound influence on aquatic ecosystems. However, the spatial distribution of ultraviolet radiation (UVR) and photosynthetically active radiation (PAR) attenuation, and the underlying mechanisms are still not fully understood. We carried out a field investigation with 60 sampling sites covering the entire Lake Qiandaohu from November 29 to December 1, 2013, during the weak stratification period to elucidate the spatial pattern and driving mechanisms. The diffuse attenuation coefficient of UVB (Kd(313)), UVA (Kd(340)) and PAR (Kd(PAR)) varied from 1.48 to 4.63 m−1, 1.09 to 3.43 m−1, and 0.26 to 0.94 m−1, respectively. The corresponding ranges for the 1% attenuation depths were from 0.10 to 3.11 m, 1.34–4.21 m and 4.87–17.58 m, respectively. Total suspended matter (TSM) concentration was highly significantly correlated with Kd(313), Kd(340) and Kd(PAR) indicating that TSM was the main driver of UVR and PAR attenuation in Lake Qiandaohu in the late autumn and early winter. TSM concentration, Kd(313), Kd(340) and Kd(PAR) had obvious horizontal spatial heterogeneity presenting a decreasing trend from the estuary area to the center area in the lake. These results suggested that the spatial distribution of TSM from the inflow drived the spatial distribution of UVR and PAR attenuation. Significantly positive correlations were also observed between the chromophoric dissolved organic matter (CDOM) absorption coefficient and Kd(313). TSM and CDOM absorption spectra showed that in the UVR waveband (350–400 nm), the mean relative contribution rates of CDOM (ag(λ)), non-algal particles (anap(λ)), phytoplankton (aph(λ)) and pure water (aw(λ)) to the total absorption were 67.5 %, 24.0 %, 5.0 % and 3.5 %, respectively. In the PAR waveband, the mean relative contribution rates of ag(λ), anap(λ), aph(λ) and aw(λ) to the total absorption were 25.4 %, 18.6 %, 9.4 % and 46.6 %, respectively. Our findings could provide support for ecological environment protection in Lake Qiandaohu considering the importance of UVR and PAR attenuation in aquatic ecosystems.

In engineering practice, it is a common that rocks are subjected to cyclic loading. The mechanical properties of rock materials under tiered, single-level, and multi-level cyclic load regimes (i.e., with different frequency, minimum stress, and amplitude) were numerically investigated by using a dynamic constitutive model for rock materials. A comparison between these loads from the aspects of stress-strain curve, modulus, damage, and strength was undertaken. The results indicate that the model can effectively reflect the different mechanical properties of rock materials under different cyclic load regimes. Under the action of tiered and multi-level cyclic loading, the area and width of the hysteresis loops become larger with increasing applied stress, but the slope of stress-strain curve, area and width of the hysteresis loops, maximum strain, and the irreversible deformation vary under different loads. The loading deformation modulus decreases with the increase of applied stress and the reductions therein are different when subjected to tiered, single-level, and multi-level cyclic loading. With increasing applied stress, the damage evolution in rock specimens subjected to tiered cyclic loading present an increasing trend and the trend likes an approximately inverted “s” -shape. Under multi-level cyclic loading, the damage variables increase rapidly at the first level, then become relatively stable and increase slowly as the applied stress increases. Furthermore, the peak strength of rock differs under different load regimes, and results indicate that cyclic loading has both strengthening and damaging effects on rock strength.

River discharge carries suspended matter into lakes, reservoirs, estuaries, and coasts, resulting in obvious plumes in river mouths. River plumes are more likely to form in valley reservoirs due to the steep slopes in the basin, which may accelerate fluvial transport from upstream to the river mouth, causing a considerable particles load and increasing the appearance times and scale of river plumes during rainfall events. Information on the intensity and evolution of river plumes in valley reservoirs has important implications for understanding nearshore geomorphological processes and dynamics in the water quality surrounding river mouths. Taking the Xin’anjing Reservoir, a typical deep valley reservoir, as a case study, a plume index based on the relative reflectance height in the red band of HJ-1 A/B images was first proposed. Subsequently, we used seventeen HJ-1 A/B images during 10 heavy rainfall events from 2009 to 2014 to characterize the spatial–temporal variability in river plumes and illustrate the relation of the river plumes and total suspended matter (TSM) concentration to the amount of rainfall. The results indicated that 10 heavy rainfall events caused different plume areas varying from 41.26 to 148.12 km2, with an average area of 76.45 ± 35.03 km2. Significant positive correlations were observed between plume areas, TSM concentrations and rainfall amount (P

Underwater light attenuation plays an important role in modulating aquatic ecosystems and is considered a sentinel of climate change and human activity. However, knowledge of the long-term exposure of underwater ultraviolet radiation (UVR) in aquatic ecosystem is still very limited. We carried out extensive UVR measurements in different seasons in five lakes at different altitudes, collected long-term Secchi disk depth (SDD) data, developed the models between UVR diffuse attenuation coefficient (Kd) and SDD, and further assessed the long-term underwater UVR exposure. Observation results from five lakes including 259 samples showed large spatial variabilities of Kd(313) (UVB) from 0.83 to 5.91 m−1 and Kd(340) (UVA) from 0.51 to 4.67 m−1. Chromophoric dissolved organic matter (CDOM) absorption coefficients were significantly correlated with Kd(313) and Kd(340). Thus, the effects of climate change and human activity on CDOM abundance, source and composition may significantly alter UVR attenuation in aquatic environments. The long-term underwater UVR exposure, which was estimated from significant positive correlations between 1/SDD and Kd(313) and Kd(340), and incident UVR, significantly decreased in Lake Fuxianhu, Lake Erhai, and Lake Qiandaohu. The regime shift from clear water state to turbid state in Lake Erhai around 2001–2003 dramatically decreased underwater UVR exposure. In conclusion, increasing UVR attenuation played a more important role in determining underwater UVR exposure than decreasing incident UVR with the relative contributions of 89.9% and 87.7% in Lake Fuxianhu, 98.0% and 97.7% in Lake Erhai, 94.4% and 92.5% in Lake Qiandaohu for UVB and UVA exposure, respectively. This is the first study to elucidate the long-term trend of underwater UVR exposure considering both increasing UVR attenuation and decreasing incident UVR.

Underground rock engineering projects are often subjected to cyclic loading such as earthquake, rock blasting. A suitable constitutive model for rock materials modeling the deformation failure characteristics of rock materials subjected to triaxial cyclic loading is significant when evaluating the long-term stability of the engineering. To date, however, there have been notably few studies on proposing constitutive models for rock materials under triaxial cyclic loading. The paper presents and validates the formulation of a new constitutive model able to reproduce the cyclic behavior of rock materials under triaxial cyclic loading. The constitutive model is based on the subloading surface theory and the modified cohesion weakening and frictional strengthening (CWFS) model. It contains kinematic hardening of the subloading surface, isotropic softening on the cohesion and isotropic hardening on the friction angle, and the effect of confining stress. Further, the model is numerically implemented in a self-developed finite element program using elastic prediction-plasticity correction method. In addition, the model is validated against two different rock materials (T2b marble and crystalline marble) under triaxial damage-controlled and constant amplitude cyclic compression loading. A reasonable consistency is observed between the numerical and experimental results for the stress-strain curves, the evolution of residual strain with number of cycles, degradation of strength and the effect of confining stress. It shows that the model can effectively reproduce the cumulative plastic deformation, hysteretic loop, damage and the effect of confining stress of rock materials under triaxial cyclic loading. Therefore, the proposed model can provide a helpful method to describe the main deformation and strength properties of rock materials under triaxial cyclic loading, and lays a foundation for the accurate analysis of the response of underground rock engineering under cyclic loading.

Rock materials, which are involved in a myriad of engineering projects, are often subjected to cyclic loading, such as earthquakes. Understanding the dynamic deformation properties of rock materials under cyclic loading is necessary for evaluating the stability of rock engineering structures. This study numerically investigated the influence of cyclic loading conditions (e.g., waveform, frequency, maximum loading stress and amplitude) on the deformation properties of rock samples using the finite element method (FEM). On the basis of the Drucker–Prager (D-P) yield criterion and sub-loading surface theory, a dynamic constitutive model for reproducing the hysteresis loops and the accumulative plastic deformation of rock materials subjected to cyclic loading was established, numerically implemented using FEM, and validated through comparison with experimental results on basalt and granite model materials. Then, cyclic uniaxial loading tests were simulated with a range of loading parameters, and the deformation properties of rock samples were analyzed. The results indicated that the hysteresis loops and accumulated plastic deformation of rock materials during the cyclic process can be numerically reproduced in an effective manner. The loading parameters significantly affected dynamic deformation properties such as the maximum strain, irreversible strain and hysteresis loop. The simulation results were almost consistent with the experimental results in the published literature. Therefore, through the proposed dynamic constitutive model, FEM can be used to numerically simulate the influence of cyclic loading conditions on the deformation properties of rock materials.

We have developed and validated a robust empirical model for estimating the concentrations of total suspended matter (TSM) in Lake Taihu (China), a large turbid inland water body. This model was generated using Moderate Resolution Imaging Spectroradiometer (MODIS-Aqua) medium-resolution (250 m) data gathered from 2003 to 2013 and in situ data collected from a number of cruise surveys. A strong significant correlate relationship between the in situ TSM data and the atmospherically corrected MODIS-Aqua remote sensing reflectance at the 645 nm band ( R rs (645)) was found (R 2 = 0.70, p n = 150). From these data, a local TSM model was developed for Lake Taihu. Long-term TSM distribution maps retrieved from the MODIS-Aqua data demonstrated marked temporal and spatial variations. Temporally, significant lower TSM was found in summer and autumn than in winter and spring ( p t -test). The significant seasonal variability could be attributed to sediment resuspension due to changes in the wind speed between different seasons. Lake Taihu also experiences large inter-annual variations that are primarily caused by changes in wind force over the region. In particular, the TSM in Lake Taihu from 2006 to 2008 was relatively lower than in other years, which could be explained by the lower mean wind speed during these years compared to the other years. Spatially, the TSM in the Open area, especially in the southern part of this region, was consistently higher than in other sub-regions of Lake Taihu. The coverage of submerged aquatic vegetation (SAV) generally characterized East Lake Taihu as a region with a relatively lower TSM. Lake topographic conditions, SAV, and runoff discharge jointly contributed to the spatial variations in TSM.

Photochemical reactions and microbial activity often result in chromophoric dissolved organic matter (CDOM) being lost to downstream cycles. The role of a specific lake ecosystem serving as a sink for CDOM was elucidated in Lake Taihu, China. The lake was divided into CDOM-enriched and CDOM-depleted regions based on principal component analysis (PCA) results. The spatial distribution of molecular size ( M ), spectral slope ratio ( S R ) and humification index (HIX) of CDOM suggested that CDOM in Lake Taihu was mainly from exogenous sources. Parallel factor analysis (PARAFAC) identified four components, including a microbially humic-like component (C1), two protein-like components (C2 and C3) and a terrestrial humic-like component (C4). Strong conservative mixing behaviors of C4 and C1 were observed in the lake, and River Yincun is likely responsible for high CDOM concentration in Zhushan Bay. Compared with C2, C3 seemed to be more independent of the terrestrial humic-like CDOM. HIX decreased and S R increased significantly from the CDOM-enriched region to the CDOM-depleted region ( t -test, p a (350), dissolved organic carbon (DOC) and summed fluorescence intensity of the four components in the CDOM-enriched region were significantly higher than in the CDOM-depleted region ( t -test, p 9 m 3 m − 1 yr − 1 and 16.91 × 10 3 t yr − 1 , respectively.

We characterized the composition and sources of chromophoric dissolved organic matter (CDOM) in rainwater, and assessed the relative contribution of rainwater CDOM to lake water in Lake Taihu based on rainwater collected during 35 rainfall events in 2012. Chemical analysis, ultraviolet–visible absorbance, and three-dimensional fluorescence spectroscopy were used to characterize CDOM. The CDOM absorption coefficient at 254 nm (a254) had a significant seasonal variation, with a mean of 3.67 ± 1.69 m−1 in the wet season (from April to early August), which was significantly lower than the means in the two dry seasons (8.26 ± 2.94 m−1 from January to March, and 7.60 ± 3.80 m−1 from late August to December). The mean humification index and the mean index of recent autochthonous contribution were 0.74 ± 0.48 and 1.31 ± 0.35, respectively, indicating that rainwater CDOM was dominated by an atmospheric microbial origin component. We identified four fluorescence components using parallel factor analysis modeling in the rainwater CDOM, i.e., two protein-like components (C1 and C2) and two fulvic-like components (C3 and C4), which had characteristics similar to those of protein and humic-like substances, respectively. The a254 was significantly and positively (p

A new plan quality index integrating dosimetric and radiobiological indices was proposed to facilitate the evaluation and comparison of simultaneous integrated boost (SIB) intensity modulated radiotherapy (IMRT) plans for nasopharyngeal cancer (NPC) patients. Ten NPC patients treated by SIB-IMRT were enrolled in the study. Custom software was developed to read dose-volume histogram (DVH) curves from the treatment planning system (TPS). A plan filtering matrix was introduced to filter plans that fail to satisfy treatment protocol. Target plan quality indices and organ at risk (OAR) plan quality indices were calculated for qualified plans. A unique composite plan quality index (CPQI) was proposed based on the relative weight of these indices to evaluate and compare competing plans. Plan ranking results were compared with detailed statistical analysis, radiation oncology quality system (ROQS) scoring results and physician's evaluation results to verify the accuracy of this new plan quality index. The average CPQI values for plans with OAR priority of low, normal, high, and PTV only were 0.22 ± 0.08, 0.49 ± 0.077, 0.71 ± 0.062, and -0.21 ± 0.16, respectively. There were significant differences among these plan quality indices (One-way ANOVA test, p < 0.01). This was consistent with statistical analysis, ROQS results and physician's ranking results in which 90% OAR high plans were selected. Plan filtering matrix was able to speed up the plan evaluation process. The new matrix plan quality index CPQI showed good consistence with physician ranking results. It is a promising index for NPC SIB-IMRT plan evaluation.

The trophic state index (TSI) is a vital parameter for aquatic ecosystem assessment. Thus, information on the spatial and temporal distribution of TSI is critical for supporting scientifically sound water resource management decisions. We proposed a semi-analytical approach to remotely estimate TSI based on Landsat 8 OLI data for inland waters. The approach has two major steps: deriving the total absorption coefficient of optically active constituents (OACs) and building the relationship between the total absorption coefficient and TSI. First, version 6.0 of the Quasi-Analytical Algorithm (QAA_V6, developed by Zhongping Lee) was implemented with Landsat 8 OLI data to derive the total absorption coefficients of the OACs. Second, we modeled TSI using the total absorption coefficients of OACs at 440 nm based on a large in situ measurement dataset. The total absorption coefficient of OACs at 440 nm gave satisfactory validation results for modeling TSI with a mean absolute percent error of 6% and a root-mean-square error of 5.77. Then, we performed this approach in three inland waters with various eutrophic statuses to validate its results, and the approach demonstrated a robust and satisfactory performance. Finally, an application of the approach was demonstrated in Lake Qiandaohu. Our semi-analytical approach has a sound optical mechanism and extensive application for different trophic inland waters.

To study the feasibility of using volumetric-modulated arc therapy (VMAT) to deliver whole-field simultaneous integrated boost (WF-SIB) to treat patients with nasopharyngeal cancer (NPC). WF-SIB intensity-modulated radiotherapy (IMRT) plans, one-arc WF-SIB VMAT plans, and two-arc WF-SIB VMAT plans were generated with identical objective functions for 8 patients with NPC of various stages. Isodose distributions and dose-volume histograms were evaluated. Dosimetric and biological quality indices of clinical target volume (CTV) and organs at risk (OARs) were calculated to study the optimization capability of these 3 modalities in the treatment of patients with NPC. The optimization time, delivery time, required monitor units (MUs), and delivery accuracy were also compared to investigate the feasibility of these 3 modalities. There was no significant difference (p = 0.92) in target coverage (TC) between WF-SIB IMRT (99.00 ± 0.79) and two-arc WF-SIB VMAT (97.98 ± 1.29). However, both had higher TC than one-arc VMAT plans (89.92 ± 6.32, p < 0.01). IMRT demonstrated the best protection of the spinal cord, whereas two-arc VMAT showed the minimum Dmax to OARs. No other significant differences were observed among these 3 modalities on CTV coverage and OAR sparing. The delivery and MU efficiency of one-arc and two-arc WF-SIB VMAT were greatly improved compared with WF-SIB IMRT. The optimization time of one-arc and two-arc WF-SIB VMAT plans were 5 and 10 times greater than that of WF-SIB IMRT, respectively. The delivery accuracy of WF-SIB VMAT was not affected by the increased freedom. For patients with NPC, one-arc WF-SIB VMAT might not be able to achieve sufficient TC, whereas two-arc WF-SIB VMAT was able to achieve reasonable TC. No significant advantage on OAR protection was demonstrated by VMAT compared with IMRT. WF-SIB VMAT has significantly shorter delivery times, but WF-SIB IMRT may still be the first treatment choice for patients with NPC.

The purpose of this work was to develop and characterize a novel delivery system of post-expansile hydrogel foam aerosol of propylene glycol-embodying liposomes (PG-liposomes) (PEHFL) for vaginal drug delivery applications. Matrine (MT) was used as a model drug to investigate the vaginal mucous membrane permeation behavior of MT from PEHFL versus PG-liposomes foam aerosol (PLFA), hydrogel foam aerosol (HFA) and hydrogel (HYG). The MT loaded PG-liposomes were characterized for shape, particle size, polydispersity, zeta potential and encapsulation efficiency; the foams of PEHFL were also characterized for swelling behavior, mucoadhesive force and duration. Results revealed that: (i) the MT loaded PG-liposomes had a mean size of 122 ± 16 nm, a good polydispersity index of 0.147 ± 0.023, and exhibited a negative charge of -47.5 ± 0.4 mV, the MT entrapment capacity in PG-liposomes (was calculated as percentages of total drug) was 80.8 ± 2.6%; (ii) the foams of PEHFL had a laggingly swelling process after spurted from a sealed container, and the higher the temperature of the surrounding environment, the greater the degree of swelling, this swelling state of foams would greatly enhance drug spread uniformly in vaginal canal and contact the vaginal walls tightly; (iii) the foams of PEHFL had a mucoadhesive force about 1460 ± 123 mN/cm(2), and could sustain 85 ± 11 min in vitro; (iv) the overall mean permeated MT through unit mass of porcine vaginal tissue from PEHFL was 2.64, 2.34 and 7.59 times higher than that from PLFA, HFA and HYG, respectively (t-test, P0.05); and the quantity of MT remaining in the vaginal tissue at the end of the 12h experiment was also significantly greater (t-test, P0.05) from the PEHFL than from PLFA, HFA and HYG. All of these results indicate that the main advantages of PEHFL over conventional dosage forms are the ability to enhance the vaginal mucosa permeability of MT, spread uniformly in vaginal canal especially the highly folded epithelial surfaces, prolong the residence time at the site of administration and induce MT delayed release. In conclusion, the PEHFL may be a promising delivery system for vaginal delivery of medication.

Radix Salvia miltiorrhiza (RSM), a traditional Chinese medicinal herb, has been alleged to possess therapeutic effects against senile dementia, also known as Alzheimer's disease (AD). However, the effects of the major components in RSM on cytotoxicity induced by amyloid-β peptide (Aβ) and on acetylcholinesterase activity have not been studied in depth to date. In this report, the effects of RSM aqueous/ethanol extracts, total polyphenols, total tanshinones and 3 phenolic compounds against toxicity mediated by Aβ(25-35) were tested with PC-12 cells. The results showed that Aβ(25-35)-induced cytotoxicity was revised by RSM aqueous/ethanol extracts and total polyphenols and that danshensu and salvianolic acid B could protect PC-12 cells by blocking Aβ(25-35)-induced Ca(2+)-intake, lactate dehydrogenase release, cell viability decrease and apoptosis. In addition, the activities of RSM extracts and relevant constituents in their inhibition of acetylcholinesterase were investigated using rat brain homogenates as an enzyme resource. Galanthamine hydrobromide, an accepted acetylcholinesterase inhibitor, was employed as a positive control agent. Our preliminary studies demonstrated that RSM ethanol extract, total tanshinones, tanshinone I and dihydrotanshinone I had remarkable inhibition effects on acetylcholinesterase in vitro. These findings suggest that both tanshinones and polyphenols in RSM are the active constituents responsible for the beneficial effects of this herb in AD treatment.

Background and purpose Anatomic changing frequently occurred during fractionated radiotherapy. The aims of this study were to model the potential benefit of adaptive IMRT replanning during fractionated radiotherapy and its potential advantage over clinical outcome in patients with nasopharyngeal carcinoma. Materials and methods Thirty-three patients with repeat CT imaging and replanning were retrospectively analyzed. 66 case-matched control patients without replanning were identified by matching for AJCC stage, gender, and age. Hybrid IMRT plans were generated to evaluate the dosimetric changing. Mann–Whitney–Wilcoxon tests were used to evaluate the effect of replanning on volumetric and dosimetric outcomes within individuals. Kaplan–Meier estimators were used to estimate the survival function of patients with or without replanning. Results The mean volume of the ipsilateral and contralateral parotid glands decreased during the treatment. The hybrid IMRT plans showed decreased doses to target volumes and increased doses to normal structures in replanning. The clinical outcome comparison indicated that the IMRT replanning improved the 3years local progression–free survival for patients who had AJCC staged more than T 3 (T 3,4 N x ) and ease the late effects for patients who had large lymph nodes (AJCC stage T x N 2,3 ). Conclusion Repeat CT imaging and IMRT replanning were recommendatory for specific nasopharyngeal carcinoma patients.

In this paper, the problem on an unique equilibrium solution of the bidirectional associative memory neural networks with distributed time-varying delays is investigated via Lyapunov stability theory. By using topological degree theory and M-matrix theory, several sufficient conditions ensuring the existence, uniqueness and global asymptotic stability of equilibrium solution are derived. An illustrative example is given to demonstrate the effectiveness of the obtained results.

Nanosized cobalt aluminate (CoAl2O4) spinel powders were prepared by the sol–gel and sol–gel-hydrothermal methods using aluminum sec-butoxide, cobalt salts and nitric acid as oxides precursors to form sols and gels. The obtained powders were characterized by XRD, DSC–TGA and SEM. The structure, particle sizes and temperature of formation of the resulting CoAl2O4 phases were found to depend on the precursors and processing methods. The temperature for obtaining the blue CoAl2O4 was about 1000 °C and 250 °C by using the sol–gel and sol–gel-hydrothermal methods, respectively, and CoAl2O4 powders with a size of 50–60 nm was resulted by the sol–gel-hydrothermal processing.