Downstream Channel Research Articles

Approximate analytical solution for supercritical flow in rectangular curved channels

In this study, we present an asymptotical mathematical model and an analytical solution for a supercritical flow in curved rectangular open channels. An original approach is proposed for solving the free-surface configuration and features of the flow in the presence of cross shock waves. The two-dimensional steady depth-averaged shallow water equations are transformed into an equivalent one-dimensional (1D) unsteady flow problem and a first order approximation is then obtained using small perturbation theory. Furthermore, the 1D asymptotic model is solved analytically by Laplace integral transformation and the two-dimensional flow field solution is reconstructed according to the translating planes. The free-surface profile along the outer chute wall and downstream channel was compared with the available experimental data, and the results indicated the satisfactory agreement of the maximum flow depth, peak positions, and wavelength. The proposed approach provides accurate predictions of the flow features and it facilitates the safe design of curved channel transitions.

Design of drainage system on industrial area Kampung Cina, Dobo City, Aru Islands Regency, based on Eco drainage using with HEC-RAS 4.0

This study aim to plan a drainage system in the Industrial area of Kampung Cina Dobo City that can overcome the problems of inundation occurred. The inundation is caused by the drainage channel that has not been properly arranged and is still in the form of a natural drainage channel, most of which still use the road drainage network whose condition is not functioning properly due to sediment and garbage which results in many drainage channels being cut off. Data processing is carried out with two analyzes including hydrological analysis and hydraulic analysis. The hydraulics analysis includes channel section planning and drainage system modeling with HEC-RAS 4.0 software. In conventional drainage discharge flowing in the channel before the end of drain amounted to 1,136 m3/sec. Once added a retention pond with a capacity of 10.358 m3 with 5 scenario dimensions spillway. The results of modeling obtained by the reduction of the maximum flood flow is 1,07 ms / sec with dimensions of aperture is 8 m x 0,8 m and lower the water level in the upstream channel by 31 cm and 44 cm in the downstream channel.

Service Quality and Customer Satisfaction in Pharmaceutical Logistics: An Analysis Based on Kano Model and Importance-Satisfaction Model.

The implementation of National Health Insurance in Taiwan has affected the medical industry by significantly depleting the supply chain’s profits. Service providers in the medical industry must meet the dual-service expectation of serving as medical manufacturers with upper reaches and as suppliers in the downstream marketing channel. As a result, service providers must anticipate customer requirements, offer new service items that align with customer demands and improve the quality of existing services. This study aims to examine consumer perspectives about service satisfaction in the domestic medical industry using Kano’s two-dimensional model. In addition, it employs the importance-satisfaction model to determine service items that need improvement. The empirical findings show that consumer perceptions about service quality attributes vary and thus, service items may be categorized differently in Kano’s model. Further, the reliability of service quality significantly affects customer satisfaction. Thus, service providers can gain a competitive edge and maintain their market position by offering high value added and critical quality attributes. Finally, analyzing customer attitudes toward new service items for indifference quality will help service providers determine effective tactics in a competitive market. In general, service providers should assign higher priority to items that customers consider in need of improvement.

Imaging work and dissipation in the quantum Hall state in graphene.

Topology is a powerful recent concept asserting that quantum states could be globally protected against local perturbations1,2. Dissipationless topologically protected states are therefore of major fundamental interest as well as of practical importance in metrology and quantum information technology. Although topological protection can be robust theoretically, in realistic devices it is often susceptible to various dissipative mechanisms, which are difficult to study directly because of their microscopic origins. Here we use scanning nanothermometry3 to visualize and investigate the microscopic mechanisms that undermine dissipationless transport in the quantum Hall state in graphene. Simultaneous nanoscale thermal and scanning gate microscopy shows that the dissipation is governed by crosstalk between counterpropagating pairs of downstream and upstream channels that appear at graphene boundaries as a result of edge reconstruction. Instead of local Joule heating, however, the dissipation mechanism comprises two distinct and spatially separated processes. The work-generating process that we image directly, which involves elastic tunnelling of charge carriers between the quantum channels, determines the transport properties but does not generate local heat. By contrast, the heat and entropy generation process-which we visualize independently-occurs nonlocally upon resonant inelastic scattering from single atomic defects at graphene edges, and does not affect transport. Our findings provide an insight into the mechanisms that conceal the true topological protection, and suggest routes towards engineering more robust quantum states for device applications.

Dam Effects on Downstream Riparian Wetlands: The Nenjiang River, Northeast China

Many studies have found that damming a river can change downstream hydrology, sediment transport, channel morphology, and fish habitat. However, little is known about river dam effects on downstream riparian wetland dynamics and their quantitative relationship with hydrological alterations. In this study, hydrological time series and wetland distribution data spanning nearly 40 years (1978–2016) before and after the construction of a large dam in 2005 across the Nenjiang River in Northeast China were used to reveal the impact of dam on the downstream discharge regime and wetland degradation. Hydro-statistical and stepwise multiple regression analyses were performed to quantify the relationship of riparian wetland area with a metrics of 33 hydrological indicators. Dam construction caused decline in peak discharge, flood frequency, and magnitude. Moreover, 150 km riparian wetlands along the downstream of the dam was largely reduced. The count and duration of high flow pulses, 1-day maximum, and date of maximum discharge changed significantly after the dam construction. The hydrological changes have made a significant contribution to the 44% reduction in riparian wetlands following the dam construction. Our results indicated that hydrological alterations caused by dam regulation led to the area reduction of downstream riparian wetlands. The findings provide relevant information for developing best dam operation practices to protect and restore downstream wetland ecosystems.

Analysis of an Ecological Flow Regime during the Ctenopharyngodon Idella Spawning Period Based on Reservoir Operations

The study of fish habitats is important for us to better understand the impact of reservoir construction on river ecosystems. Many habitat models have been developed in the past few decades. In this study, a fuzzy logic-based habitat model, which couples fuzzy inference system, two-dimensional laterally averaged hydrodynamic model, and two-dimensional shallow water hydrodynamic model, is proposed to identify the baseline condition of suitable habitat for fish spawning activities. The proposed model considers the reservoir and the downstream river channel, and explores the comprehensive effects of water temperature, velocity, and water depth on habitat suitability. A real-world case that considers the Ctenopharyngodon idella in the Xuanwei Reservoir of Qingshui River is studied to investigate the effect of in- and outflow of reservoir on fish habitat and the best integrative management measure of the model. There were 64 simulations with different reservoir in- and outflows employed to calculate the weighted usable area and hydraulic habitat suitability. The experimental results show that the ecological flow for Ctenopharyngodon idella spawning can satisfy the basic demand when the reservoir inflow is greater than 60 m3/s and the reservoir outflow is greater than 100 m3/s. The habitat ecological suitability is the best when the reservoir outflow is 120 m3/s. A more reasonable and reliable ecological flow range can be obtained based on the habitat model in this paper, which provides the best scenario for water resources planning and management in the Qingshui River Basin.

Responses of channel morphology to flow-sediment variations after dam construction: a case study of the Shashi Reach, middle Yangtze River

AbstractUpstream damming has profoundly impacted downstream channel morphology by altering inflowing water and sediment conditions, which can mostly be ascribed to variations in the flow hydrograph and sediment supply regime. In this paper, channel erosion and deposition during different flow-sediment processes are quantified using a 2D hydro-morphodynamic model. Our results revealed that the net erosion mainly occurred during the flood season when the flow discharges were above 15,000 m3/s. Together, larger peak discharges and less sediment supply could produce greater net erosion. Flow hydrograph variations could alter the inundation extent, thus creating a more widespread redistribution of channel deposition and erosion and possibly causing a shift in the active channel adjustment area, where more channel scouring and siltation occurred. The channel adjustments caused by the sediment supply regime variations underwent a gradual downward propagation process, and most of the riverbed thalweg profile variations could first be observed at a very short distance from the studied reach entrance. A larger cross-sectional area and channel depth as well as a lower width-depth ratio could result from larger floods and less incoming upstream sediment load. We found that a comprehensive flow-sediment combination coefficient with a value of m ranging from 2 to 4 most appropriately reflected the post-dam flow-sediment imbalance regime at the studied reach, which implied the leading role of flow hydrograph variations in shaping channel morphology. In summary, the combined results presented herein for the Shashi Reach of the Yangtze River can provide a better understanding of the downstream morphological impacts of different flow-sediment processes caused by dam operation.

Applicability of Kinematic model for mud-flows: An unsteady analysis

The Kinematic Wave Model (KWM), representing a simplification of the Full Wave Model (FWM) under the shallow-water approximation, is often used in the one-dimensional formulation for describing the dynamics of debris/mud flood. The present work investigates the applicability conditions of the KWM to analyze mud floods, characterized by a rheological behaviour expressed through a power-law model. The study is carried out through the numerical solution of both the Full and Kinematic Wave models changing the characteristic time of hydrograph, i.e. the wave duration, imposed at the channel inlet. The predictions of the two models are compared in terms of maximum flow depth, maximum discharge and peak discharge at the downstream channel end. The study is performed for several values of the Froude (F) and the Kinematic Wave (K) numbers. Similarly to the clear-water case, present results show that higher errors in applying KWM pertain to shorter flood wave durations, but the performance of KWM appears to strongly depend on the value of the rheological index, becoming worse as the fluid rheology becomes more shear-thinning. The study furnishes applicability criteria representing a guideline for practical applications in terms of minimum wave duration above which the KWM error in reproducing the considered flood characteristics (the maximum flow depth, the maximum discharge and the peak discharge at the downstream channel end) is less or equal than 5%. Finally, it has been shown that the wave period criterion, obtained considering linearized wave dynamics, may be safely applied at least for fluid with moderate shear-thinning behavior and for moderate values of the dimensionless number KF2.

A gigabit transceiver for the ATLAS inner tracker pixel detector readout upgrade

This paper presents the design and simulation results of a gigabit transceiver Application Specific Integrated Circuit (ASIC) called GBCR for the ATLAS Inner Tracker (ITk) Pixel detector readout upgrade. GBCR has four upstream receiver channels and a downstream transmitter channel. Each upstream channel operates at 5.12 Gbps, while the downstream channel operates at 2.56 Gbps. In each upstream channel, GBCR equalizes a signal received through a 5-meter 34-American Wire Gauge (AWG) twin-axial cable, retimes the data with a recovered clock, and drives an optical transmitter. In the downstream channel, GBCR receives the data from an optical receiver and drives the same type of cable as the upstream channels. The output jitter of an upstream channel is 26.5 ps and the jitter of the downstream channel after the cable is 33.5 ps. Each upstream channel consumes 78 mW and each downstream channel consumes 27 mW. Simulation results of the upstream test channel suggest that a significant jitter reduction could be achieved with minimally increased power consumption by using a Feed Forward Equalizer (FFE) + Decision Feedback Equalization (DFE) in addition to the linear equalization of the baseline channel. GBCR is designed in a 65-nm CMOS technology.

Abstract 4048: REAlease® technology: Controlled release of antibody-fluorochrome conjugates for maximal flexibility in flow sorting and fluorescence microscopy applications

Abstract Multi-parameter immunofluorescent labeling is the method of choice for the flow-based sorting of targeted cell populations from heterogeneous samples. However, existing antibody-fluorochrome conjugates used for flow sorting limit the types of downstream analyses that can be applied to the isolated cells, as their continued presence on the cells blocks specific cellular epitopes and restricts the choice of downstream fluorescence detection channels. Herein, we present a new type of antibody-fluorochrome conjugates that facilitates a highly specific multi-parameter cell staining for flow sorting as well as subsequent complete release of the conjugate probes from the sample. These new conjugates rely on recombinantly engineered antibody fragments that individually possess low epitope binding affinities. A tailor-made covalent conjugation chemistry allows for their multimerization as well as fluorochrome labeling, generating fluorescent probes comparable to conventional antibody conjugates. Importantly, upon addition of a release reagent, the antibody-fluorophore conjugates can be rapidly released from the cell surface. Accordingly, previously blocked epitopes are free for re-labeling, which provides maximal flexibility for renewed epitope targeting in downstream applications. As many targeted cell populations require multi-parameter detection of several antigens for their isolation, the recombinant engineered antibodies were conjugated with different fluorochromes. The versatility of this technology is presented in multi-parameter panels enabling clear distinction and discrimination of different cell populations of different starting material, e.g. peripheral blood and tumor cells. The applicability of the new REAlease® antibody fluorochrome conjugates is also demonstrated by flow sorting of human naïve regulatory T cells. In addition, we show that the fast and efficient releasability of the new conjugates can serve as an optimal basis for cyclic immunofluorescence microscopy using a new MACSima™ imaging platform, which permits cell analysis with potentially unlimited number of parameters. Citation Format: Jennifer Pankratz, Sabine Schmachtenberg, Nicole Jansen, Marie Hansen, Susanne Krauthäuser, Ali Kinkhabwala, Karolina Schlegel, Svenja Meiler, Christiane Siewert, Alina Bartholomäus, Dmytro A. Yushchenko, Christian Dose. REAlease® technology: Controlled release of antibody-fluorochrome conjugates for maximal flexibility in flow sorting and fluorescence microscopy applications [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4048.

Enhanced stability of flows through contraction channels: Combining shape optimization and linear stability analysis

The first flow bifurcation, in channels with a sudden geometry contraction, is controlled through shape optimization to delay the onset of asymmetry. First, we confirm the existence of a pitchfork type bifurcation instability, already reported in similar geometries. The global mode responsible for this bifurcation leads to asymmetric flow for Reynolds numbers beyond a critical value. Second, we propose a global shape optimization methodology to introduce small modifications in the channel geometry that lead to flows with enhanced stability. Our results include three contraction ratios C = 2, 4, and 8, where C is the ratio of upstream to downstream channel widths. The shape optimization aims at minimizing the growth rate of the unstable mode responsible for asymmetry. Sensitivity analysis is used to find an appropriate geometry parametrization, which is defined through super-elliptic curves, and limited to small deformations. Additionally, a dynamically updated surrogate model (based on radial basis functions) is developed to drive the optimization. This substitutes expensive function evaluations, each requiring the solution of a steady Navier-Stokes base flow computation and a solution of an eigenvalue problem (linear stability analysis). Finally, a mode tracking algorithm identifies the eigenmode responsible for the onset of asymmetry during the optimization. The optimized geometries show rounded corners and are stable for Reynolds numbers well beyond the original values. For all contraction ratios, the critical Reynolds number increases by at least 7.9 times with respect to the original values. Three-dimensional simulations confirm that the optimized geometry is more stable than the original when periodic boundaries are used on the side walls. When comparing the drag of the optimized geometry to the original, we obtain a reduction of at least 64%.

Understanding the geomorphic consequences of enhanced overland flow in mixed agricultural systems: sediment fingerprinting demonstrates the need for integrated upstream and downstream thinking

Sediment fingerprinting approaches help improve our understanding of the on- and off-site impacts of soil erosion in the critical zone, including upstream and downstream ecosystem services and the wider implications for food, water and energy security. This study evaluates the impact of intensive agricultural land management practices on overland flow generation with attention to process controls on sediment production and delivery from both hillslope and in channel sources. This study applied a sediment fingerprinting approach in the Merriott Stream catchment in rural Somerset, UK. Major and minor element geochemistry were determined for sources under cultivated (n = 12) and grazing (n = 12) land management regimes plus channel bank erosion (n = 10) for a notably incised downstream drainage network. These were compared to both suspended sediment (n = 3) and channel bed sediment (n = 4) sampled along the stream network. Sediment sources were apportioned with the MixSIAR mixing model. The dominant contributor to suspended sediment captured in transit was cultivated land (ca. 60–90%). The dominant contributor to channel bed sediment in the lower catchment was channel bank erosion (ca. 50–75%). The former was linked to enhanced overland flow and increased erodibility of cultivated soils. The latter was linked to contemporary incision of the stream network driven by a more erosive hydrological regime (i.e. increased magnitude and frequency of runoff events) which was causing localized erosion and bank failure. These in-channel processes of incision and bank failure were exacerbated by a lack of vegetation on the banks due to winter die-back of the invasive weed Himalayan Balsam. This exposes the bank surface to direct fluvial scour under winter high flows and prevents the establishment of a perennial root structure from native plants that typically plays an important role in bank stability. This study has demonstrated the need to consider a holistic catchment-based approach to understanding and managing bank erosion and, in particular, it highlights the need for integrated upstream and downstream thinking where distal runoff processes lead to increased potential for downstream channel instability.

Bank Processes and Revetment Erosion of a Large Lowland River: Case Study of the Lower Tisza River, Hungary

Stone and concrete revetments are widely constructed to control bank erosion and thus stabilize river banks. The consequences include accelerated erosion at unrevetted downstream channel sections and in-channel incision at revetted sections. The studied section of the Tisza River (Hungary) was revetted along 49% of its banks in the 20th century with stepped-block and placed-rock revetments. We therefore aimed (1) to study the effects of revetment constructions on channel processes and (2) to evaluate the state and collapse of revetments using a DEM of the channel and ADCP measurements. In the late 19th century, the river had an equilibrium meandering channel, with alternating eroding and aggrading banks. Currently, erosional processes dominate. Thus, 65% of the total channel length is affected by bank erosion. The revetments reduced the active lateral erosional processes only temporarily, as 58% of the revetments, mainly placed-rock, are already damaged. The flow characteristics at the revetted sections were found to depend on the rate and type of revetment collapse. Large pools developed in front of the revetments, playing an important role in initiating their erosion. The placed-rock revetments can collapse by slides or by stones falling into the pool one-by-one. In this case, a knickpoint develops, propagating upstream. Thus, the collapse and accelerated bank erosion also propagate upstream. The increased hazard created by the failure of the revetments requires the re-planning of bank stabilization practices.

Tackling reservoir siltation by controlled sediment flushing: Impact on downstream fauna and related management issues

Sediment flushing can tackle reservoirs siltation and improve sediment flux through dammed rivers. However, the increase of the sediment loading below the dam can trigger a suite of undesired ecological effects in the downstream river reaches. To limit these drawbacks, sediment flushing can be controlled, by jointly regulating the sediment concentration of the evacuated water and the streamflow in the downstream channel. In this paper, we report on ten controlled sediment flushing operations (CSFOs), carried out between 2006 and 2012 in the central Italian Alps, at four hydropower reservoirs. These CSFOs displayed specific common traits: (i) Limits were set by the local environmental authorities concerning the allowable suspended sediment concentration. (ii) Reservoirs were fully drawn-down, earth-moving equipment was used to dislodge sediment, and the downstream water discharge was increased, compared to baseflow, by operating upstream intakes. (iii) Abiotic and biotic measurements in selected downstream reaches (before, during, and after the CSFOs) represented an integral part of the operations. In contrast, significant differences characterize the hydropower facilities (elevation and storage of reservoirs, in particular) as well as the basic CSFOs parameters (i.e., season, duration, mass and grain-size of the evacuated sediment, suspended sediment concentration). The macroinvertebrate assemblages resulted noticeably impacted by the CSFOs. In the short term, a significant density drop was observed, slightly influenced by the extent of the perturbation. In contrast, the latter appeared to control the assemblages contraction in terms of richness, according to the different sensitivity to sediment stress of the different taxa. The time employed to recover pre-CSFO standard ranged from few months to just under one year, and the related patterns would seem mostly correlated to the flushing season and to further site specificities. The density of trout populations was impacted as well, thus suggesting the adoption of mitigating strategies as removal by electrofishing before, and repopulation after the CSFO.

Experimental Study of Flow Structure Characteristics for a T-Junction Duct With Horizontal Vanes

An experimental study is carried out to investigate the flow characteristics of the trailing edge of the horizontal vanes mounted at the branch entrance of a T-junction duct by means of particle image velocimetry (PIV). The measured region starts at the trailing edge of the vanes and ends at about 1.26D (hydraulic diameter) length at downstream of the branch duct. The velocity field is obtained across a number of vertical height planes (z/D = ±0.2, 0, and −0.4) under different flow conditions (cross velocity: uc = 30–50 m/s; velocity ratio: R = 0.08–0.18). The instantaneous flow results show that Kelvin-like vortices with counter-clockwise direction appear at the heights of z/D = ±0.2 and 0, and that a separation bubble is formed at the upper wall of the branch duct at the same heights, respectively. As for near wall z/D = −0.4, one large vortex is observed at the downstream channel, but the separation bubble vanishes as the branching Reynolds number is increased to 3.6 × 104. The time-average flow field is slightly different from that of instantaneous flow field. In addition, the vorticity distribution indicates that two significant vortex sheet layers with negative and positive values are found at the high velocity ratio or high cross velocity, and the normalized vorticity strength increases with increasing velocity ratio and decreases with increasing cross velocity except at z/D = −0.4.

PENGARUH VEGETASI TERHADAP TAHANAN ALIRAN PADA SALURAN IRIGASI

Irrigation channel in D.I. Timbang Deli, Deli Serdang district Sumut province has a total area of 520 Ha and a 5000 meter long secondary channel. Irrigation channel in D.I. Timbang Deli overgrown vegetation at the base and wall of the channel so it is expected to affect roughness. The objective of the study was the flow resistance with the variation of vegetation volume to the variation of the discharge. The method used in this study is field observation by measuring flow velocity, flow depth and vegetation volume (VT) on trapezoidal tract width of 3.75 m and height of 0.90 m along 154 m. Measurements were performed on 3 points of upstream, middle and downstream channels and 5 transverse dots X1 through X5 4 times with D1 debit variation of 1.32 m³/s and D2 of 0.98 m³/s. The dominant vegetation channels are rigid. Measurement velocity using current meter while for vegetation volume (VT) using grid method. The results showed that vegetation volume VT0 (0,00 m³/0,00%), VT1 (52,417 m³/21,14%), VT2 (70,7921 m³/24,51%) and VT3 (83,053 m³/30,42%). It is seen that the increase in vegetation volume can affect the flow resistance. The result of measurement increased the resistance of flow to VT0 0,052, VT1 equal to 0,062 with percentage 16,13%, VT2 equal to 0,108 with percentage 51,85% and VT3 equal to 0,122 with percentage 57,37% atD1. Meanwhile, at D2 there is an increase of flow resistance to VT0 by 0,044, VT1 is 0,052 with percentage 15,38%, VT2 equal to 0,058 with percentage 24,14% and VT3 equal to 0,070 with percentage 37,14%. This shows that the flow resistance VT0 is smaller than the flow resistance VT1, VT2 and VT3. From the above results are expected to conduct O and P channels by surrounding communities and related government.

Dam Operation for Mitigating Ice Jam Flooding Risks under the Adjustment of River Channel-Forms: Implications from an Evaluation in the Ningxia-Inner Mongolia Reach of the Upper Yellow River, China

Dam operation has been widely deployed to mitigate the risks of ice jam flooding, but it may result in a decrease in the discharging capacities of downstream river channels. The Ningxia-Inner Mongolia reach of the Huanghe River (Yellow River) has historically suffered numerous disasters caused by ice jam flooding, and three large dams have been jointly operated to mitigate such risks since 1968. Whilst the resultant significant increases in both the annual runoff and mean water temperature during the ice jam flooding seasons helped to shorten the freezing-up duration and reduce the thickness of the ice cover, a significant channel shrinkage occurred in the reach when the dam operation took place under the input of a relatively larger amount of sediment from the upstream. In the new flow regime that commenced in 2008, a detailed examination of the river channel-form adjustments and the resultant changes to the discharging capacities identified a slight increase in the discharging capacity of the channel along the entire study reach. This was mainly due to a significantly smaller amount of sediment load being carried by a slightly increased annual runoff. Whilst it was demonstrated that the dam operation was still an effective means for mitigating the risk of ice jam flooding in the Ningxia-Inner Mongolia reach under the new flow regime, care needs to be taken when the favorable flow-sediment condition changes. Furthermore, the effectiveness of the dam operation appeared to vary significantly at the channel sections of different planforms; thus, more detailed studies are required.

NO/cGMP/PKG activation protects Drosophila cells subjected to hypoxic stress

The anoxia-tolerant fruit fly, Drosophila melanogaster, has routinely been used to examine cellular mechanisms responsible for anoxic and oxidative stress resistance. Nitric oxide (NO), an important cellular signaling molecule, and its downstream activation of cGMP-dependent protein kinase G (PKG) has been implicated as a protective mechanism against ischemic injury in diverse animal models from insects to mammals. In Drosophila, increased PKG signaling results in increased survival of animals exposed to anoxic stress. To determine if activation of the NO/cGMP/PKG pathway is protective at the cellular level, the present study employed a pharmacological protocol to mimic hypoxic injury in Drosophila S2 cells. The commonly used S2 cell line was derived from a primary culture of late stage (20–24 h old) Drosophila melanogaster embryos. Hypoxic stress was induced by exposure to either sodium azide (NaN3) or cobalt chloride (CoCl2). During chemical hypoxic stress, NO/cGMP/PKG activation protected against cell death and this mechanism involved modulation of downstream mitochondrial ATP-sensitive potassium ion channels (mitoKATP). The cellular protection afforded by NO/cGMP/PKG activation during ischemia-like stress may be an adaptive cytoprotective mechanism and modulation of this signaling cascade could serve as a potential therapeutic target for protection against hypoxia or ischemia-induced cellular injury.

Variation and Driving Factors of Water Discharge and Sediment Load in Different Regions of the Jinsha River Basin in China in the Past 50 Years

The Jinsha River is the main source of sediment in the Yangtze River Basin. The variation of water discharge and sediment load not only affects the operation of the cascade reservoirs in the basin but also change the water and sediment conditions into the Three Gorges Reservoir. The Jinsha River Basin is divided into six regions based on the measured data of hydrological stations. Herein, the variation regularity and driving factors of water discharge and sediment load in the Jinsha River Basin are analyzed in the past 50 years using the Mann–Kendall and Rank Sum Test. Results show that the source of water and sediment in the Jinsha River Basin is different, and the abrupt and trend changes of water discharge and sediment load in different regions are evident different. Changes in precipitation, water and soil conservation projects, and the construction of reservoirs are the main driving factors of sediment load variation. The average annual sediment reduction load in the Jinsha River from 1998 to 2015 is approximately 99.57 × 106 t/y, of which the contributions of water discharge change and human activities to sediment load are 18.9% and 81.1%, respectively. The reduction of sediment load in the Jinsha River Basin can result in evident decrease in the sedimentation of cascade reservoirs, erosion of the downstream channel of the river, and considerable reduction of sediment load into the Three Gorges Reservoir.

Quantitative analysis of the macro-geomorphic evolution of Buyuan Basin, China

Buyuan River, the largest tributary within the Chinese Lancang-Mekong River region downstream of the Jinghong Dam, plays a crucial role in river function and ecosystem service of the Lancang-Mekong River. The geomorphic evolution of a basin exerts a key control on riverine sediment input and transport. In this study, the geomorphic characteristics of Buyuan Basin are analyzed using morphological parameters, hydrodynamic parameters and the stream power river incision model. The results show that: 1) The slight north-south difference of channel density is most likely due to lithology and independent of tectonic activity and climate. 2) The weak tectonic activity and the low hypsometric integral (HI) value suggest that the macroscopic landform condition limits erosion and sediment production. 3) The logarithmic longitudinal profile of the main channel defends that the upstream sediments generated by erosion are easily deposited in the downstream channel, rather than being transported directly into the Lancang-Mekong River. 4) Approximately 74% of the reaches have annual average stream power less than 500 W·m−1. The narrow variation ranges of stream power in 50% of the river channel indicate relatively stable hydrodynamic environment. 5) Stream erosion and tectonic activity make the longitudinal profiles of the main channel and most tributary channels unstable. The wide range (between 22.01 and 45.58 with θ=0.43) of steepness index (ksn) of longitudinal profiles implies differential uplift in the basin.