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As a key link between top‐down regulators and bottom‐up factors, zooplankton responds sensitively to environmental variations and provides information on the ecological state of freshwater systems. Although the response of zooplankton to anthropogenic pressures and fluctuating natural conditions, such as nutrient loading and climate change, has been extensively examined, findings have varied markedly. The mechanistic basis for the correlation between environmental variability and the zooplankton community is still debated, particularly for subtropical eutrophic lakes. We used two methods to analyze physicochemical and selected biological variables derived from long‐term monitoring of Lake Taihu, a subtropical shallow lake in China. We first applied random forest regression to examine how changes in zooplankton were related to a set of environmental variables on interannual time scales. Then we used the results to guide the construction of a conceptual model for piecewise structural equation modeling (pSEM) to quantify more precisely the zooplankton–environment relationship. Zooplanktivorous fish and nutrient concentrations were the most important predictors of long‐term trends in zooplankton in RF regression. Intensification of planktivorous fish predation led to a lower zooplankton biomass and smaller individuals through the removal of larger crustaceans. Moreover, suppression of zooplankton can in part be explained by increases in inedible algae, triggered by a combination of reduced nutrient concentrations and weakened grazer control. These results were also confirmed in the pSEM, which further indicated that top‐down regulators might be more important than bottom‐up factors for the zooplankton community in Lake Taihu. Our results suggest that stocking of filter‐feeding fish in the lake did not meet the expectation that they would control algae, but that the use of biomanipulation measures considering both water quality and fishery management seems promising. This study offers insights into how indicator metrics of zooplankton can improve our understanding of the associations between plankton communities and ecosystem alterations. [ABSTRACT FROM AUTHOR]

Automated spraying is among the priorities in the development of China's shipbuilding industry today with the increased consciousness of product quality, processing efficiency and environmental friendliness. The research topic is derived from a true case of a shipyard. A mobile truss platform hoisted with a six-axis robot is deployed for large ship blocks spraying. This paper studies the trajectory planning problem of spraying. A spray distribution model based on β distribution is established, NSGA-III is applied to minimize working time and the variance of paint film thickness, and maximize paint utilization. [ABSTRACT FROM AUTHOR]

This paper presents a new approach to coupling line balancing and buffer allocation for stochastic mixed-model assembly line. Three types of complexity are defined, that are time diversity complexity for single station, time diversity complexity for a whole line, and time stochastic fluctuations complexity. An integrated optimization model for line balancing and buffer allocation is established with the objectives of maximizing productivity, minimizing complexity and total buffer capacity. Then an improved genetic algorithm is applied to solve the model. Finally, the effectiveness of the method is verified by an example of a mixed-model assembly line. [ABSTRACT FROM AUTHOR]

According to the problem of trajectory planning for collaborative welding robot with multiple manipulators which is applied in dual-beam laser welding of aircraft double curved panel, the multi-manipulator kinematics model is constructed based on Devanit-Hartenberg (D-H) method, and the solution of inverse kinematics is deduced through the specific algebraic method. In addition, the motion law of each joint variable is obtained on the basis of the trajectory planning method for the continuous path. Finally, the correctness of inverse kinematics algorithm and the effectiveness of trajectory planning for the modified robot are verified by ADAMS simulation. [ABSTRACT FROM AUTHOR]

A collaborative welding platform consists of a XYZ-mobile truss, a 3R (revolute joint) clamping robot and a dual-arm welding robot. Based on Denavit-Hartenberg (D-H) method, the analytical inverse kinematics solution of the platform is obtained. Dual-arm coordination is a technical difficulty in robot control field. Focusing on self-collision problem during dual-arm robot motion planning, this paper proposes a new obstacle avoidance algorithm based on Rapidly Exploring Random Tree (RRT) algorithm. Setting searching area founded on artificial potential field (APF) algorithm and adopting note-pruning strategy achieves high searching efficiency. Simulation results verify the correctness of kinematics analysis and self-collision detection algorithm. [ABSTRACT FROM AUTHOR]

Sertraline (SER) is one of the most commonly detected antidepressants in the aquatic environment that can negatively affect aquatic organisms at low concentrations. Despite some knowledge on its acute toxicity to fish, the effects of chronic SER exposure remain poorly understood along with any underlying mechanisms of SER-induced toxicity. To address this knowledge gap, the effects of chronic exposure to three SER concentrations from low to high were investigated in zebrafish. Juvenile zebrafish were exposed to three concentrations of 1, 10, or 100 μg/L of SER for 28 d, after which indicators of oxidative stress and neurotoxicity in the brain were measured. Superoxide dismutase (SOD) activity was significantly enhanced by SER at 1 up to 100 μg/L, and catalase (CAT) activity was significantly induced by SER at 1 or 10 μg/L. The activity of acetylcholinesterase (AChE) was significantly induced by 10 and 100 μg/L of SER, and the serotonin (5-HT) level was significantly increased by all three concentrations of SER. To ascertain mechanisms of SER-induced toxicity, transcriptomics was conducted in the brain of zebrafish following 100 μg/L SER exposure. The molecular signaling pathways connected with circadian system and the immune system were significantly altered in the zebrafish brain. Based on transcriptomic data, the expression levels of six circadian clock genes were measured, and three genes were significantly altered in relative abundance in fish from all experimental treatments with SER, including cryptochrome circadian regulator 2 (cry2), period circadian clock 2 (per2), and period circadian clock 3 (per3). We hypothesize that the circadian system may be related to SER-induced neurotoxicity and oxidative stress in the central nervous system. This study reveals potential mechanisms and key events (i.e., oxidative stress and neurotoxicity) associated with SER-induced toxicity, and improves understanding of the molecular and biochemical pathways putatively perturbed by SER. [Display omitted] • Sertraline caused slight oxidative stress in juvenile zebrafish. • Sertraline induced neurotoxicity in juvenile zebrafish. • Pathways related to circadian system and immune system were perturbed by sertraline. • The expression levels of genes related to circadian rhythm were affected by sertraline. [ABSTRACT FROM AUTHOR]

Cyanobacterial blooms producing toxic metabolites occur frequently in freshwater, yet the environmental behaviors of complex cyanobacterial metabolites remain largely unknown. In this study, the seasonal and spatial variations of several classes of cyanotoxins (microcystins, cylindrospermopsins, saxitoxins) and taste-and-odor (T&O) compounds (β-cyclocitral, β-ionone, geosmin, 2-methylisoborneol) in Lake Taihu were simultaneously investigated for the first time. The total cyanotoxins were dominated by microcystins with concentrations highest in November (mean 2209 ng/L) and lowest in February (mean 48.7 ng/L). Cylindrospermopsins were abundant in May with the highest content of 622.8 ng/L. Saxitoxins only occurred in May (mean 19.2 ng/L) and November (mean 198.5 ng/L). Extracellular T&O compounds were most concentrated in August, the highest being extracellular β-cyclocitral (mean 240.6 ng/L) followed by 2-methylisoborneol (mean 146.6 ng/L). Environment variables play conflicting roles in modulating the dynamics of different groups of cyanotoxins and T&O compounds. Total phosphorus (TP), total nitrogen (TN), chlorophyll- a and cyanobacteria density were important factors affecting the variation of total microcystins, β-cyclocitral and β-ionone concentrations. In contrast, total cylindrospermopsins, 2-methylisoborneol and geosmin concentrations were significantly influenced by water temperature and TP. There was a significant and linear relationship between microcystins and β-cyclocitral/β-ionone, while cylindrospermopsins were positively correlated with 2-methylisoborneol and geosmin. The perceptible odors may be good indicators for the existence of cyanotoxins. Hazard quotients revealed that potential human health risks from microcystins were high in August and November. Meanwhile, the risks from cylindrospermopsins were at moderate levels. Cylindrospermopsins and saxitoxins were first identified in this lake, suggesting that diverse cyanotoxins might co-occur more commonly than previously thought. Hence, the risks from other cyanotoxins beyond microcystins shouldn't be ignored. This study also highlights that the necessity for further assessing the combination effects of these complex metabolites. [Display omitted] • Diverse cyanotoxins and odorants were identified in Lake Taihu for the first time. • Environment factors play conflicting roles in driving different class of metabolites. • The perceptible odors may be good indicators for the existence of cyanotoxins. • The human health risks of cyanotoxins beyond microcystins shouldn't be ignored. [ABSTRACT FROM AUTHOR]

Planktonic and benthic cyanobacteria blooms are increasing in frequency in recent years. Although many studies have focused on the effects of purified toxins or cyanobacteria extracts on fish developments, the more complex impacts of cyanobacteria cells on fish populations are still considered insufficient. This study compared the toxicological effects of harmful planktonic Microcystis and benthic Oscillatoria on zebrafish (Danio rerio) early stages of development. Zebrafish embryos, at 1–2 h post fertilization (hpf), were exposed to 5, 10, and 20 × 105 cells/mL Microcystis (producing microcystins) or Oscillatoria (producing cylindrospermopsins) until 96 hpf. The results indicated that the effects of benthic Oscillatoria on embryonic development of zebrafish were different from those of planktonic Microcystis. Reduced hatching rates, increased mortality, depressed heart rates and elevated malformation rates were observed following exposures to increased concentrations of Microcystis , whilst Oscillatoria exposures only caused yolk sac edemas. Exposure to a high concentration of Microcystis induced severe oxidative damage, growth inhibition and transcriptional downregulations of genes (GH , GHR1 , IGF1 , IGF1rb) associated with the growth hormone/insulin-like growth factor (GH/IGF) axis. Although Oscillatoria exposure did not affect the body growth, it obviously enhanced the antioxidant enzyme activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) and up-regulated the expressions of several oxidative stress-related genes. Discrepancies in the developmental toxicity caused by Microcystis and Oscillatoria may not only attributed to the different secondary metabolites they secrete, but also to the different adhesion behaviors of algal cells on embryonic chorion. These results suggested that harmful cyanobacteria cells could influence the successful recruitment of fish, while the effects of benthic cyanobacteria should not be ignored. It also highlighted that the necessity for further investigating the ecotoxicity of intact cyanobacterial samples when assessing the risk of cyanobacterial blooms. Image 1 • Microcystis exposure caused growth inhibition and oxidative damage. • Disruption of GH/IGF axis contributed to the growth inhibition. • Oscillatoria exposure did not influence body growth, but induced oxidative stress. • Cyanotoxins alone in the present study cannot fully explain the observed effects. • The ecological risks of intact cyanobacterial cells should deserve more attention. A brief summary: The toxic effects of harmful cyanobacteria on zebrafish embryonic development are not only related to the known cyanotoxins, but also to the species of cyanobacteria cells. [ABSTRACT FROM AUTHOR]

Sertraline (SER) is one of the most frequently detected antidepressant drugs in aquatic environments. However, knowledge regarding SER-induced behavioral alterations in fish is insufficient, as well as the mechanisms underlying SER-induced toxicity. The present study aimed to determine behavioral and molecular responses in larval fish following SER exposure with a focus on its mode of action. Zebrafish embryos (~6 h-post-fertilization, hpf) were exposed to one of three concentrations of SER (1, 10, 100 μg/L) for 6 days, respectively. Evaluated parameters included development, behavior, transcripts related to serotonin signaling, serotonin levels, and acetylcholinesterase activity. Accelerated hatching of zebrafish embryos was observed for those fish exposed to 100 μg/L SER at 54 hpf. Locomotor activity (e.g. distance moved and mobile cumulative duration) was significantly reduced in larval zebrafish following exposure to 10 and 100 μg/L SER. Conversely, larval fish showed increased dark-avoidance after exposure to 1–100 μg/L SER. Of the measured transcripts related to serotonin signaling, only serotonin transporter (serta) and serotonin receptor 2c (5-ht2c) mRNA levels were increased in fish in response to 10 μg/L SER treatment. However, serotonin levels were unaltered in larvae exposed to SER. There were no differences among groups in acetylcholinesterase activity at any concentration tested. Taking together, the results evidenced that exposure to SER alters behavioral responses in early-staged zebrafish, which may be related to the abnormal expression of 5-ht2c. This study elucidates molecular responses to SER and characterizes targets that may be sensitive to antidepressant pharmaceuticals in larval fish. ga1 • Exposure to sertraline accelerated the hatching of zebrafish embryos. • Sertraline reduced larval locomotor behaviors. • Low concentrations of sertraline increased dark-avoidance behavior of larval zebrafish. • Sertraline up-regulated the expression of serta and 5-ht2c. [ABSTRACT FROM AUTHOR]