Peak Occurrence Time Research Articles

Spatiotemporal variations of groundwater and gully impact in two peatland watersheds in the Upper Yellow River, Qinghai‐Tibet Plateau

AbstractThe spatiotemporal variability of groundwater level is an important property of peatland hydrology that directly alternates water storage. Nonetheless, the current understanding of the variations of groundwater level over long periods of time remains limited. In this study, we investigated two peatland watersheds (0.151 km2 for Watershed 1 and 0.844 km2 for Watershed 2) in the Zoige Basin in the upper watershed of the Yellow River to monitor temporal variability of groundwater level using self‐recorded water loggers over 4 years (2017–2021). The main results demonstrate that (1) groundwater level variations were controlled by gully drainage in sites adjacent to the gully but were more affected by rainfall in sites distant from the gully. The groundwater level near the gully downcut was lower than that near the gully without complete downcutting through the pear layer, with a maximum difference of 58.3 cm, indicating the longitudinal effect of groundwater level in the watershed. (2) Because the rainfall had a lag effect on the groundwater level, the length of lag gradually decreased with increased rainfall intensity (i.e., the lag time for sites distant from the gully was about 18 min shorter than that of sites close to the gully in Watershed 1). (3) The peak values of the groundwater level occurred simultaneously with the maximum and minimum rainfall in Watershed 2, and the peak occurrence time was related to the ratio of precipitation to evaporation. In the downstream sites, the groundwater level fluctuated more than the upstream ones in Watershed 2. Moreover, the average groundwater level in the upstream sites was 14.3 cm higher than that of the middle ones, indicating a decreasing trend of water storage along the gully. (4) The differences in groundwater level between wet and dry seasons were clear, but the difference was smaller in the upstream sites due to limited gully incision and higher water storage within the peat layer. Additionally, groundwater level changes were more extreme on rainy days during both the wet and dry seasons, but the different intensities of rainfall resulted in stable groundwater in the dry season and an oscillating groundwater level in the wet season in Watershed 2. This study uncovers the groundwater dynamics in the two peatland watersheds, which is of great significance for understanding runoff variation, ecohydrological processes, and wetland shrinkage.

The influence of change in river networks on waterway connectivity and flooding processes

ABSTRACT Urbanization disrupts river networks, alters waterway connectivity, and elevates flood control pressure. Quantitatively assessing river network changes and their impact on waterway connectivity and flooding processes is imperative. We constructed a waterway connectivity evaluation model and a hydrologic–hydrodynamic model to assess the river network, the waterway connectivity and the flooding change in the Qinhuai River Basin, and used scenario analysis to determine the effectiveness of different topology changes. The results showed a 0.09 decline in connectivity from 2000 to 2010, which led to a peak occurrence time 1 h earlier, an increase in peak discharge by 2.59 m3/s and a rise in peak water level by 51 mm. Scenario analysis demonstrated that adding tributaries can enhance both connectivity and flood resilience. Increasing river width effectively reduces peak water levels while minimally affecting connectivity. Extending river length has a negligible effect on peak water levels but may decrease waterway connectivity.

Rolling forecast of snowmelt floods in data-scarce mountainous regions using weather forecast products to drive distributed energy balance hydrological model

Snowmelt flood forecasting plays a crucial role in water resource management and utilization in arid regions. However, the accuracy of current snowmelt flood forecasts falls short of requirements due to complex mountainous terrain and limited observational data. In this study, We conducted a snowmelt flood simulation and forecasting experiment in a mountainous watershed in northern Xinjiang. First, we used site observations, ERA5-land reanalysis data and WorldClim data to produce historical meteorological forcing, calibrated the VIC-CAS model and improved routing model using historical observed runoff data, and conducted a detailed simulation of the hourly snowmelt flood process in the basin. Then, the latest grid forecast weather product developed by the China Meteorological Administration was integrated into the system to conduct a rolling forecast test of the snowmelt floods in the next 72 h during the snowmelt period in 2023. The remotely sensed snow cover and the freezing level measured by the sounding balloon were assimilated into the model in real time to correct the deviation of runoff simulation. The results show that during the model calibration period, the KGE of the simulated monthly runoff in the Kayertes River basin (KRB) from 2006 to 2011 was 0.83 and the NSE was 0.86. In the continuous hourly runoff simulation during the 2022 snowmelt period, the model well captured the intraday fluctuations of snowmelt runoff in the KRB, with the daily peak flow error within ± 20 % and the peak occurrence time controlled within ± 4 h. In the rolling forecast test in 2023, the daily peak flow error is within ± 20 % (the peak occurrence error during the peak period is even controlled within ± 5 %), and the peak occurrence time is within ± 4 h. Real-time assimilation of freezing level measured by sounding balloons and remotely sensed snow cover can effectively correct the deviations in simulated temperature and snow cover. This study can provide insights for runoff prediction in other high-altitude mountainous areas where data are scarce.

Characteristic fingerprint spectrum of α-synuclein mutants on terahertz time-domain spectroscopy

α-Synuclein, a presynaptic neuronal protein encoded by the SNCA gene, is involved in the pathogenesis of Parkinson’s disease. Point mutations and multiplications of α-synuclein (A30P and A53T) are correlated with early-onset Parkinson’s disease characterized by rapid progression and poor prognosis. Currently, the clinical identification of SNCA variants, especially disease-related A30P and A53T mutants, remains challenging and also time consuming. This study aimed to develop a novel label-free detection method for distinguishing the SNCA mutants using transmission terahertz (THz) time-domain spectroscopy. The protein was spin-coated onto the quartz to form a thin film, which was measured using THz time-domain spectroscopy. The spectral characteristics of THz broadband pulse waves of α-synuclein protein variants (SNCA wild type, A30P, and A53T) at different frequencies were analyzed via Fourier transform. The amplitude A intensity (AWT, AA30P, and AA53T) and peak occurrence time in THz time-domain spectroscopy sensitively distinguished the three protein variants. The phase φ difference in THz frequency domain followed the trend of φWT > φA30P > φA53T. There was a significant difference in THz frequency amplitude A′ corresponding to the frequency ranging from 0.4 to 0.66 THz (A′A53T > A′A30P > A′WT). At a frequency of 0.4–0.6 THz, the transmission T of THz waves distinguished three variants (TA53T > TA30P > TWT), whereas there was no difference in the transmission T at 0.66 THz. The SNCA wild-type protein and two mutant variants (A30P and A53T) had distinct characteristic fingerprint spectra on THz time-domain spectroscopy. This novel label-free detection method has great potential for the differential diagnosis of Parkinson’s disease subtypes.

Analysis of spatial and seasonal variations of Haemaphysalis longicornis population based on field survey collected under different habitats and years

AbstractTicks are vectors of disease‐causing pathogens and are found on domestic and wild animals; thus, they are also vectors of significant human diseases. For this reason, pre‐emptive measures to prevent tick‐borne diseases are necessary in the form of exploring their major habitats, population increase period, and factors affecting their population growth, all of which indicate the purpose of this study. In the study, a variation of Haemaphysalis longicornis, a major vector of fever‐causing conditions, was statistically analyzed to identify the spatial and climatic factors affecting the time‐dependent variations of its population. The survey occurred in different habitats (grassland, mixed forest, deciduous forest, and coniferous forest) in South Korea. In addition, we fitted a phenology model by using a probability function to find the peak occurrence time annually. As a result, the numbers of adults and nymphs were found to be related to temperature and relative humidity and their population peaked at the end of May in all habitats except deciduous forests. This study is expected to provide information on habitat types, times, and climate patterns that require attention to help control H. longicornis populations.

Prediction of liver metastasis and recommended optimal follow-up nursing in rectal cancer.

We aimed to analyze and investigate the clinical factors that influence the occurrence of liver metastasis in locally advanced rectal cancer patients, with an attempt to assist patients in devising the optimal imaging-based follow-up nursing. Between June 2011 and May 2021, patients with rectal cancer at our hospital were retrospectively analyzed. A random survival forest model was developed to predict the probability of liver metastasis and provide a practical risk-based approach to surveillance. The results indicated that age, perineural invasion, and tumor deposit were significant factors associated with the liver metastasis and survival. The liver metastasis risk of the low-risk group was higher at 6-21 months, with a peak occurrence time in the 15th month. The liver metastasis risk of the high-risk group was higher at 0-24 months, with a peak occurrence time in the 8th month. In general, our clinical model could predict liver metastasis in rectal cancer patients. It provides a visualization tool that can aid physicians and nurses in making clinical decisions, by detecting the probability of liver metastasis.

Flood forecasting based on radar precipitation nowcasting using U-net and its improved models

Accurate and timely short-term precipitation nowcasting is important for achieving reliable flood forecasting. The data-driven approaches have performed well in radar echo extrapolation to nowcast precipitation. In this paper, U-Net and its improved models, including SmaAt-Unet, Nested-Unet, and U-Net 3Plus were applied to perform radar echo extrapolation and precipitation nowcasting for 0.5 h, 1 h, and 2 h lead times of typical rainfall processes. The nowcasted precipitation was used as input to the HEC-HMS hydrological model for flood forecasting to compare the effect of different structural improvements to U-Net on the accuracy of flood forecasting. The results demonstrated that Nested-Unet and U-Net 3Plus aided in enhancing the accuracy of the extrapolation of moderate intensity radar echoes. With fewer discrepancies and better correlation with measured rainfall, the U-Net and U-Net 3Plus precipitation nowcasting results also produced improved flood forecasting outcome. The precipitation nowcasting and flood forecasting for SmaAt-Unet were slightly worse than other models; the relative errors of both flood peak and depth for Nested-Unet at 0.5 h lead time were less than 20 %, showing a good performance. Moreover, in a separate control experiment, the accuracy of the echo extrapolation was significantly decreased when convolutional block attention module (CBAM) was added to each model. However, all models have better extrapolation accuracy than the basic ConvLSTM. In general, Nested-Unet and U-Net 3Plus were helpful to improve the accuracy of precipitation nowcasting and flood forecasting, and the forecasted flood with 0.5 h and 1 h lead times could match the actual flood processes, but the peak discharge from nowcasting with 2 h lead time were severely underestimated, while the peak occurrence time could be forecasted correctly. These conclusions and attempts can provide effective guidelines for regional precipitation nowcasting and flood forecasting.

Stochastic Flood Simulation Method Combining Flood Intensity and Morphological Indicators

The existing flood stochastic simulation methods are mostly applied to the stochastic simulation of flood intensity characteristics, with less consideration for the randomness of the flood hydrograph shape and its correlation with intensity characteristics. In view of this, this paper proposes a flood stochastic simulation method that combines intensity and morphological indicators. Using the Foziling and Xianghongdian reservoirs in the Pi River basin in China as examples, this method utilizes a three-dimensional asymmetric Archimedean M6 Copula to construct stochastic simulation models for peak flow, flood volume, and flood duration. Based on K-means clustering, a multivariate Gaussian Copula is employed to construct a dimensionless flood hydrograph stochastic simulation model. Furthermore, separate two-dimensional symmetric Copula stochastic simulation models are established to capture the correlations between flood intensity characteristics and shape variables such as peak shape coefficient, peak occurrence time, rising inflection point angle, and coefficient of variation. By evaluating the fit between the simulated flood characteristics and the dimensionless flood hydrograph, a complete flood hydrograph is synthesized, which can be applied in flood control dispatch simulations and other related fields. The feasibility and practicality of the proposed model are analyzed and demonstrated. The results indicate that the simulated floods closely resemble natural floods, making the simulation outcomes crucial for reservoir scheduling, risk assessment, and decision-making processes.

Improvement and evaluation of hydrodynamic conditions in plain regional drainage systems by artificial lakes: a case study of Xinxiang Economic Development Zone, China.

With the development of the city, people pay more attention to the ecological construction of the city. The objective of this work was to study the effect of artificial lakes on hydrodynamic conditions in urban drainage systems. With Arcgis and the advantage of SWMM in analyzing the impact of the rainfall process on urban runoff, the urban flooding model of "pipe network + river network + artificial lake" was established in the study area. Two scenarios were set up with and without the presence of artificial lakes, and comparative analyses were conducted under the different intensities of rainfall (0.5a, 1a, 2a, 5a, 10a, 20a). The results show that under certain rainfall conditions, the presence of the artificial lake increases the peak flow and rate of upstream streams and decreases the flow and rate of downstream streams in the regional drainage system. The duration of the peak flow rate in the upstream channel increases, and the flow rate curve becomes flat during the confluence; the flow rate in the downstream section decreases, and the magnitude of the peak flow rate change decreases, and a more obvious horizontal section appears. The time of peak occurrence in the downstream river is earlier. The hydrodynamic impact on the downstream channel is more significant. The improvement of hydrodynamic conditions of the drainage system by the artificial lake helps to optimize the layout of low impact development (LID) measures in the study area and also guides ecological construction in other cities.

Application of residence time distribution (RTD) to enhance the performance of perforated baffled constructed wetland under unsteady flow

The perforated baffle can significantly enhance the performance of the constructed wetland. In the present study, the effects of perforation shape, number of baffles, baffle position and perforation location on the flow pattern of wetlands were investigated using NaCl impulse-response tracer test, and perforated baffles were used to improve the nitrogen removal rate of the constructed wetland. The perforated baffle optimizes the flow pattern by reducing the peak height of the RTD curve and delaying the peak occurrence time. Triangle perforation exhibits better flow pattern optimization due to its smaller area. When the inlet flow rate is 100 mL/min, the mean residence time (Tm) increases by 0.25 h. The position of the perforated baffle has a more significant effect on the flow pattern, being able to better extend hydraulic residence time (HRT) when located at the height of H/2 substrate. In addition, the perforation locations of two adjacent baffles are not on the same vertical line, which can increase the horizontal water flow velocity and improve the space utilization of the wetland. Compared to the control check constructed wetland (CKCW) without baffles, the perforated baffled constructed wetland (PBCW) exhibited a higher NH4+-N removal rate of 84.53 ± 7.48 % during stable operation. This is mainly because the perforated baffle improves the utilization of dissolved oxygen (DO) while improving the water flow distribution and extending the HRT. In conclusion, perforated baffles have considerable potential to alleviate shock loading and enhance the performance of constructed wetlands.

Application of a Fractional Instantaneous Unit Hydrograph in the TOPMODEL: A Case Study in Chengcun Basin, China

The movement of water flow usually has history and path dependence. Fractional calculus is very suitable for describing the process with memory and hereditary properties. In this study, the order of the differential equation in the Nash confluence system was extended from integer order to fractional order. On the basis of the Laplace transform, the fractional instantaneous unit hydrograph was obtained, which was used to describe the long-term memory of the basin confluence system. Furthermore, the enhanced TOPMODEL (FTOP) model was obtained by applying the fractional instantaneous unit hydrograph as the surface runoff calculation. Taking Chengcun Basin in China as an example, the FTOP model was used to simulate the daily runoff and 22 floods from 1989 to 1996. The simulation results were compared with two original TOPMODEL models (the NTOP and ITOP models). The results show that in the daily runoff simulation, the Nash–Sutcliffe efficiency (NSE), relative error (RE), and root mean square error (RMSE) of the FTOP model were 0.82, −11.14%, and 15.25 m3/s, respectively, being slightly better than the other two TOPMODEL models. According to the hydrologic frequency curve, the measured daily runoff was divided into different flow levels. It was found that the FTOP model can improve the simulation effect of the medium-flow (frequency between 10% and 50%) and low-flow (frequency more than 50%) sections to a certain extent. In the flood simulation, the average runoff depth relative error (RDRE), peak discharge relative error (PDRE), peak occurrence time error (POTE), and NSE of 22 floods were 1.99%, 14.06%, −1.27, and 0.88, respectively, indicating that the simulation effect had been improved. Especially in NSE, the improvement was more prominent, meaning that the FTOP model can better simulate the flooding process. However, the flood peak and runoff depth simulation effect were not significantly improved. These conclusions indicate that the confluence method using the fractional instantaneous unit hydrograph as the TOPMODEL model can improve the simulation effect.

Study on the Dynamics of Stem Sap Flow in Minqin Wind and Sand Control Haloxylon ammodendron Forest, China

In this study, we obtained real-time data on the stem fluid flow of Haloxylon ammodendron in the growing season in Minqin, China, based on thermal diffusion (TDP) monitoring technology, and analyzed the dynamic changes of stem fluid flow in it to provide important supporting evidence for understanding the water consumption of H. ammodendron during its growth. The results indicate that the fluid flow in the stem of the H. ammodendron increases with increasing growth age and also decreases as the H. ammodendron grows older and declines. The average daily sap flow rates of H. ammodendron stems were 0.956, 1.059, 1.460 and 0.570 cm3·(cm2·h)−1 at 5, 10, 15 and 20 years, respectively, and the cumulative sap flow masses during the growing season from May to October were 610.173, 423.386, 1041.186 and 430.212 kg, respectively. H. ammodendron stem sap flow increases with the thickening of H. ammodendron’s ground diameter. The average daily sap flow rate of H. ammodendron stems at different stem levels ranged from 0.276 to 2.132 cm3·(cm2·h)−1, and the cumulative sap flow mass during the growing season ranged from 121.656 to 1722.810 kg. The larger the diameter of the H. ammodendron at different forest ages, the earlier the sap flow initiation time and the higher the peak. The stem flow initiation time was 7:00–8:00, and the average daily maximum fluid flow rate was 2.493–5.536 cm3·(cm2·h)−1, with the peak occurrence time advancing with age. The sap flow variation of H. ammodendron at different stand ages reflects the water-consuming process of H. ammodendron growth and its response to a drought environment, while the sap flow variation of H. ammodendron at different diameter classes shows that the individual growth differences of H. ammodendron also yield obvious competitive advantages. The results of the analysis can provide theoretical support for the estimation of ecological water use in desert H. ammodendron sand-fixing forests.

Dynamic fracture analysis in nonhomogeneous piezoelectric materials with a new domain-independent interaction integral

In order to comprehend and forecast the dynamic fracture behaviors of piezoelectric materials, dynamic intensity factors (IFs) are crucial fracture parameters. It is a challenge to effectively calculate the dynamic IFs of the piezoelectric materials containing complicated elastic and/or electric interfaces. For piezoelectric materials with nonhomogeneous properties or even random interfaces, a dynamic domain-independent interaction integral (DII-integral) is established to assess the dynamic stress intensity factors (SIFs) and the dynamic electric displacement intensity factor (EDIF). Furthermore, it is theoretically demonstrated that random interfaces in the integration domain have no effect on the efficiency of the DII-integral and it does not include any derivatives of electromechanical characteristics. The extended finite element method (XFEM) is integrated with the dynamic DII-integral method to study typical cracked piezoelectric specimens exposed to electromechanical impact loads. A wonderful consistency is obtained by evaluating the current results with the relevant literature. Good domain-independence of the proposed dynamic I-integral is verified for nonhomogeneous and discontinuous piezoelectric properties (relative deviation < 1 %). The numerical simulations show the amplitudes of the dynamic SIFs and EDIF are highly affected by the polarization direction. In general, the density has an obvious influence on the peak occurrence time of the dynamic SIF and EDIF. The dielectric permittivity impacts the EDIF evidently, however, the SIF marginally. On the contrary, the piezoelectric coefficient obviously impacts the SIF and EDIF. The elastic stiffness has a considerable impact on the SIF but a minor one on the EDIF.

Simulation and Prediction of the Impact of Climate Change Scenarios on Runoff of Typical Watersheds in Changbai Mountains, China

Simulating the hydrological process of a river basin helps to understand the evolution of water resources in the region and provides scientific guidance for water resources allocation policies between different river basins and water resources management within the river basin. This paper provides a scientific basis for the sustainable development of regional water resources and an accurate grasp of the future change trend of runoff by analyzing the hydrological process response of runoff in typical watersheds in Changbai Mountains, China, to climate change. The applicability of the HEC-HMS (The Hydrologic Engineering Center’s-Hydrologic Modeling System) hydrological model in the watershed is verified by calibrating and verifying the daily rainfall-runoff process in the watershed during the wet season from 2006 to 2017. The daily rainfall data of the two scenarios SSP2-4.5 and SSP5-8.5 under the BCC-CSM2-MR model in the 2021–2050 CMIP6 plan were downscaled and interpolated to in-basin stations to generate future daily precipitation series to predict runoff response to future climate change. The daily rainfall data of the two scenarios were downscaled and interpolated to the stations in the basin to generate future daily rainfall series to predict the runoff response under future climate changes. The average certainty coefficient of the HEC-HMS model for daily runoff simulation reached 0.705; the rainfall in the basin under the two climate scenarios of SSP2-4.5 and SSP5-8.5 in the next 30 years (2021–2050) will generally increase, and rainfall will be more evenly distributed in the future; the outlet flow of the basin will increase during the wet season (June–September) in the next 30 years, but it is lower than the historically measured value; the peak flow of the future will appear at most in August and September. The peak flow current time mostly appears in July and August. The time of peak occurrence has been delayed.

A Novel Bimodal Forecasting Model for Solar Cycle 25

Abstract In this paper, a novel bimodal model to predict a complete sunspot cycle based on comprehensive precursor information is proposed. We compare the traditional 13 month moving average with the Gaussian filter and find that the latter has less missing information and can better describe the overall trend of the raw data. Unlike the previous models that usually only use one precursor, here we combine the implicit and geometric information of the solar cycle (peak and skewness of the previous cycle and start value of the predicted cycle) with the traditional precursor method based on the geomagnetic index and adopt a multivariate linear approach with a higher goodness of fit (&gt;0.85) in the fitting. Verifications for cycles 22–24 demonstrate that the model has good performance in predicting the peak and peak occurrence time. It also successfully predicts the complete bimodal structure for cycle 22 and cycle 24, showing a certain ability to predict whether the next solar cycle is unimodal or bimodal. It shows that cycle 25 is a single-peak structure and that the peak will come in 2024 October with a peak of 145.3.

Experimental study on the propagation characteristics of hydrogen/methane/air premixed flames in a narrow channel

This work is focused on the explosion characteristics of premixed gas containing different volume fractions of hydrogen in a narrow channel (1000 mm × 50 mm × 10 mm) under the circumstance of stoichiometric ratio. The ignition positions were set in the closed end and the middle of the pipeline respectively. The results showed that when the gas was ignited at the pipeline closed end, the propagating flame was tulip structure for different premixed gas. When the hydrogen volume fraction was less than 40%, the flame propagation speed increased significantly with the rise of hydrogen volume fraction, and the overpressure peak also appeared obviously in advance. However, when the volume fraction of hydrogen was more than 40%, the increase of flame propagation speed and the overpressure peak occurrence time varied slightly. Furthermore, when the ignition position was placed in the middle of the pipeline, the flame propagation speed propagating to the opening end was much faster than that propagating to the closing end, and there was no tulip shape when the flame propagates to the opening end. The flame propagating to the closed end appeared tulip shape under the influence of airflow, and high-frequency flame oscillation occurred during the propagation. This work shows that the hydrogen volume fraction and ignition position significantly affected the flame structure, flame front speed, and explosion overpressure.

Uncertainty of storm surge forecast using integrated atmospheric and storm surge model: a case study on Typhoon Haishen 2020

ABSTRACT Hindcast experiments and pseudo-forecast experiments considering Typhoon Haishen (2020) were conducted using an atmospheric (WRF)-storm surge (GeoClaw) coupled model and a storm surge model with a parametric typhoon model. A series of simulations of the coupled model were used to quantify the error sources of the typhoon track and intensity in the forecast errors of storm surges. The results revealed that the typhoon track forecast had a larger error source for the storm surge forecast for the maximum surge height than the typhoon intensity. Furthermore, the parametric Holland typhoon model used in practice has an overestimation trend compared to the coupled model, and the parametric Holland typhoon model using WRF output was able to forecast the storm surge height near the typhoon (western Kyushu area) and its peak occurrence time accurately. However, the forecast accuracy tended to decrease as the distance from the typhoon to the target location increased. The pseudo-ensemble simulation of the storm surge forecast using forecast error information was conducted considering the uncertainty of the typhoon track forecast. The 20 ensemble forecast simulations revealed that the perturbed typhoon track simulation can increase the possibility of capturing the peak time of the storm surge.

Changes in Flood Regime of the Upper Yangtze River

River flooding affects more people worldwide than other natural hazards. Thus, analysis of the changes in flood regime caused by global warming and increasing anthropogenic activities will help us make adaptive plans for future flood management. The nonstationary flood behavior in the upper Yangtze River was examined comprehensively in terms of trend, change point, and periodicity with co-usage of different methods. Results show that there are decreasing tendencies in the corresponding series of annual maximum flood peak flow and flood volume in four out of six control stations, except Pingshan and Wulong stations in the Jinsha River and the Wu River, respectively, and the flood peak occurrence time appears earlier mostly. The uniformity of flood process increases in four main tributaries, while it decreases in mainstream of the Yangtze River (Yichang and Pingshan stations). The rates of both rising limb and recession limb of all the typical flood process flowing through the six stations were analyzed. 77.8% of the rates of rising limb decrease, while 61.1% of the rates of recession limb increase, which is almost consistent with the variation reflected by the uniformity. The change points of most evaluation indicators happened in 1970s–1990s. The first main periodicity of evaluation indicators in Yichang is about 45 years, while that of other stations is about 20 years. Invalidity of stationarity in the flood series can be attributed to the intensified construction on major water conservancy projects, changes of underlying surface, and influences of climatic variables. The contributions of both climatic control and the Three Gorges Dam (TGD) to the variation of the annual flood peak in Yichang station were further quantitatively evaluated, which has verified that the construction of the TGD has played a positive role in peak-flood clipping.

Application of environmental DNA technology in natural reproduction of the four major Chinese carps in Yichang section of Yangtzi River, China

We explored the sample collection and DNA extraction method of environmental DNA (eDNA) technique. Droplet digital PCR (ddPCR) was used to detect the eDNA concentration of the four major Chinese carps in different water layers and different cross-sections of Yichang section of Yangtze River trunk stream. We analyzed the relationship between eDNA concentration and density of egg and fry, and explored the feasibility of using eDNA technique to monitor the natural reproduction of the four major Chinese carps. Compared with the results from traditional survey methods, the eDNA concentration of the four major Chinese carps was extremely significantly correlated with egg and fry density. The maximum concentration was consistent with the peak occurrence time of egg and fry, suggesting that eDNA technique could predict the fishcrowd behavior for spawning. The investigation of cross-section eDNA concentration during two consecutive years suggested that the range of fish spawning ground was 4.5 km upstream to 1 km downstream of Yuyangxi. The predicted spawning ground was located within the range estimated by traditional methods from the lower part of Carmine Dam to Honghua Tuo. Our results indicate that eDNA technique, as a new ecological investigation method, could more accurately determine the distribution of fish with a certain population size, and thus with a good application prospect.

Peripheral immune circadian variation, synchronisation and possible dysrhythmia in established type 1 diabetes

Aims/hypothesisThe circadian clock influences both diabetes and immunity. Our goal in this study was to characterise more thoroughly the circadian patterns of immune cell populations and cytokines that are particularly relevant to the immune pathology of type 1 diabetes and thus fill in a current gap in our understanding of this disease.MethodsTen individuals with established type 1 diabetes (mean disease duration 11 years, age 18–40 years, six female) participated in a circadian sampling protocol, each providing six blood samples over a 24 h period.ResultsDaily ranges of population frequencies were sometimes large and possibly clinically significant. Several immune populations, such as dendritic cells, CD4 and CD8 T cells and their effector memory subpopulations, CD4 regulatory T cells, B cells and cytokine IL-6, exhibited statistically significant circadian rhythmicity. In a comparison with historical healthy control individuals, but using shipped samples, we observed that participants with type 1 diabetes had statistically significant phase shifts occurring in the time of peak occurrence of B cells (+4.8 h), CD4 and CD8 T cells (~ +5 h) and their naive and effector memory subsets (~ +3.3 to +4.5 h), and regulatory T cells (+4.1 h). An independent streptozotocin murine experiment confirmed the phase shifting of CD8 T cells and suggests that circadian dysrhythmia in type 1 diabetes might be an effect and not a cause of the disease.Conclusions/interpretationFuture efforts investigating this newly described aspect of type 1 diabetes in human participants are warranted. Peripheral immune populations should be measured near the same time of day in order to reduce circadian-related variation.Graphical abstract