The Monthly Variation Tendency of Microcystin-LR Levels in The Huangpu River (China) by Applications of ELISA and HPLC

In this study, the contents of microcystin-LR (MC-LR) of Microcystis aeruginosa cultures in the laboratory and natural water samples from the Huangpu River in different seasons were detected through enzyme-linked immunosorbent assay (ELISA) and high-performance liquid chromatography (HPLC), respectively. Excellent correlation between the two methods was obtained (R2 > 0.99). ELISA was a reliable and simple method with high reproducibility (coefficient of variation < 25%) and satisfactory recovery for the monitoring of low levels of MC-LR. MC-LR concentrations in Huangpu River varied with the seasonal variation,which peaked in August with the temperature over 30°C and then gradually declined with the decreasing temperature after August. The highest MC-LR concentration in the Huangpu River was below the WHO drinking water quality standard (1 ug/L). These results indicated that warm temperature accelerated the MC-LR synthesis and release, and it is necessary to regularly monitor the MC-LR levels, especially during the high algae period in summer. ELISA can be applied to detect the low levels of MC-LR in the field without complex treatment, avoiding the samples from denaturation and degradation during the transportation. Hence, ELISA is a better alternative of HPLC when HPLC is unavailable, especially when rapid testing is required in routine MC-LR analysis.

Effect of pulsed magneto oscillation and phosphorus on microstructure and tensile properties of as-cast Al-25% Si alloy

The effect of pulsed magneto oscillation (PMO) on the microstructure and tensile properties of Al-25% Si alloys with and without phosphorus addition was investigated. When PMO was applied to the melt during solidification, the results show that the PMO treatment is an effective method for refining the primary Si of Al-25% Si alloy with and without phosphorus addition. The morphology of primary Si was considerably refined via coarse dendritic and polygon shape to fine and regular block under the PMO treatment, and the average size of primary Si was refined to 30.8 μm and 45.3 μm under the optimal processing conditions for the alloy with and without phosphorus addition, respectively. The tensile strength and elongation of the alloys first increased and then decreased with rise of current. Analysis shows that application of PMO decreases Gibbs free energy and critical nucleus radius of the Al-25% Si alloy during solidification. The nucleation rate first increased and then decreased with increasing PMO intensity. The variation tendency of average number of primary Si per unit area is consistent with the theory analysis.

Information Measures of Knowledge Contribution: A New Method to Measure Knowledge Contribution in Collaborative Knowledge Building: An Information Theory Perspective

The measurement of knowledge contribution in collaborative knowledge building is an important research topic in computer-supported collaborative learning. The information measures of knowledge contribution based on information theory are proposed in this study, which includes two measures: amount of information and information gain. Discourse data collected from a collaborative knowledge building activity were analyzed to validate these measures. The results showed that our information measures can complement the traditional behavioral. With the help of the two measures, community-level variation tendency and individual-level knowledge contribution characteristics could be analyzed in collaborative knowledge building activities. A log function was used to fit the community knowledge variation tendency to measure the convergence of knowledge building. Students were clustered into five types according to their behaviors and contributions in collaborative knowledge building. Both teachers and researchers can benefit from these two information measures by using them in practice.

A macro traffic flow model with headway variation tendency and bounded rationality

The rapid adoption of sensor technology has upgraded the vehicular communication capacity, which enables the drivers to predict the traffic state (e.g. headway variation tendency (HVT)) based on the current traffic information. Meanwhile, in practice, the drivers would exhibit bounded rationality behavior in that they often perceive and respond to acceleration/deceleration only when the headway variation exceeds a certain threshold. The collective effect may greatly affect the driving behavior and traffic flow performance. In this study, we innovatively model the traffic flow macroscopically considering HVT and bounded rationality effect in the context of continuum model. Based on the linear stability theory, the stability condition of the above model is obtained. The KdV-Burgers equation of the model is derived to describe traffic jam propagation mechanism near the neutral stability line by applying the reductive perturbation method in nonlinear stability analysis. Results show that the HVT and bounded rationality behavior have a great impact on the traffic congestion and energy consumption.

Variation of LED Display Color Affected by Chromaticity and Luminance of LED Display Primary Colors

In recent years, the effect of LED display is increasingly important in the LED display field. Primary colors’ chromaticity and luminance of LED display as crucial elements influence the LED display color. Therefore, there is a need for color mapping algorithms that indicate the relationship between primary colors and display color’s chromaticity and luminance. In this paper, two mathematical models have been developed. One has shown the display color’s chromaticity and luminance affected by luminance of primary colors change. The other one has shown a complicated relationship that primary color is mixed by other primary colors to change chromaticity first and then the mixed primary is used as “new LED primary color.” In both mathematical models, CIE x ∗ y ∗ Y color space was used as the mutual color space; thus, there was a specific variation tendency of colors with luminance or chromaticity of primary colors change in this color space. The newly designed mathematical models can consistently guide us how to acquire the desired display color by changing luminance or chromaticity of primary colors. Therefore, it has important engineering application value.

Influence of Scour Development on Turbulent Flow Field in Front of a Bridge Pier

This study concerns the turbulent flow field influenced by the scour development around a bridge pier. The scour hole evolution as well as the temporal variation of scour depth around the pier were firstly analyzed. Subsequently, the flow fields in front of the pier at different instants during the scour process were measured using particle image velocimetry (PIV). It shows that the scour depth at the pier front exceeds that of the pier side at the later scouring stage. The temporal development of scour depth can be well predicted by a simple practical engineering model based on an exponential function with a change in the two adjustable coefficients. The flow field indicates that with the development of scour hole, the downward flow in front of the pier becomes more prominent, meanwhile the flow becomes more turbulent. The variation tendency for both velocities and turbulence intensities along the streamwise direction in front the pier shows similarity. The Reynolds shear stress generally increases with developing scour hole, and the region with large value enlarges and moves upstream of the scour hole.

Mass and stiffness identification of particle beam system based on a dynamic effective mass method

We perform an investigation on identification of the complicated particle beam system, focusing on the occurrence and the mechanism of the resonant peaks. The concept concerning dynamic effective mass of the particle beam system is put forward, which realizes the decoupling of mass, stiffness, and damping. Excitation strategies, such as constant amplitude variable frequency sweep, are used during the testing process. The relationships between the dynamic effective mass of the particle beam system and the excitation frequency are recorded to study the mass and stiffness effects of the system. The results show that the variation of system stiffness and the negative mass are the main reasons for occurrence of resonant peaks. On the basis of the variation tendency of stiffness, we infer that the particle flow state transits from solid state to liquid state and thus, the whole frequency band is divided into three regions with an increase in excitation frequency. Within the region of solid state, resonant frequencies can be estimated roughly, which also proves reliability of the inference. The influence of burial depth and force amplitude on stiffness and mass of the system is investigated to reveal the tendency of all peaks and explain the jump phenomenon roughly.

The variation tendency of serum C-reactive protein is a good marker to predict postoperative complications after laparoscopic gastrectomy for adenocarcinoma of esophagogastric junction

Background: Postoperative complications (PCs) after laparoscopic gastrectomy with mediastinal lymph nodes resection for adenocarcinoma of esophagogastric junction (AEG) prolonged the time of hospitalization and increased mortality rate. Early diagnosis of PCs was of great importance. This retrospective study aimed to investigate whether the variation tendency of serum C-reactive protein can be used as an early marker to predict major postoperative complications after laparoscopic gastrectomy for AEG.Methods: Data for patients underwent laparoscopic gastrectomy for AEG, from January 2015 to March 2020, were retrospectively analyzed. The area under the receiver operating characteristic (ROC) curve (AUC) was used to determine diagnostic accuracy of inflammatory markers. The optimal cutoff values were calculated by maximizing Youden’s index. Univariate and multivariate logistic regression analyses were performed to identify risk factors for PCs of grade III or more，according to the Clavien-Dindo classification. Results: A total of 114 patients were analyzed, of whom 21 (18.4%, 95% CI 11.4-25.4 %) developed major PCs, including anastomotic leakage in 13. The ratio of CRP level on postoperative day 3 to day 2 (POD3/2 CRP) provided the best diagnostic accuracy (AUC 0.903, 95% CI 0.814-0.993, p＜0.001). Proximal gastrectomy (OR 8.224, 95% CI 1.976-34.234, p=0.004) and operation time ≥360 minutes (OR 6.753, 95% CI 2.037-22.395, p=0.002) were identified as significant independent risk factors for major PCs.Conclusions: The POD3/2 CRP was the best marker to predict PCs after laparoscopic gastrectomy for AEG.

The Variation Tendency of Serum C-Reactive Protein is A Good Marker to Exclude Anastomotic Leakage after Laparoscopic Gastrectomy for Adenocarcinoma of Esophagogastric Junction

Backgroud:Esophagojejunal anastomotic leakage (EJAL) after laparoscopic gastrectomy with mediastinal lymph nodes resection for adenocarcinoma of esophagogastric junction (AEG) constituted the most common and serious postoperative complications (PCs). Early diagnosis of EJAL was of great importance. This retrospective study aimed to investigate whether the variation tendency of serum C-reactive protein can be used as an early marker to exclude EJAL after laparoscopic gastrectomy for AEG.Methods:Data for patients underwent laparoscopic gastrectomy for AEG, from January 2015 to March 2020, were retrospectively analyzed. Diagnostic accuracy was determined by the area under the receiver operating characteristic curve. Univariate and multivariate logistic regression analyses were performed to identify risk factors for PCs of grade II or more，according to the Clavien-Dindo classification. Results:A total of 114 patients were analyzed, of whom 21 (18.4%, 95% CI 11.4-25.4 %) developed major PCs, including anastomotic leakage in 13. The ratio of CRP level on postoperative day 3 to day 2 (POD3/2 CRP) provided the best diagnostic accuracy (AUC 0.903, 95% CI 0.814-0.993, p＜0.001). Proximal gastrectomy (OR 8.224, 95% CI 1.976-34.234, p=0.004) and operation time ≥360 minutes (OR 6.753, 95% CI 2.037-22.395, p=0.002) were identified as significant independent risk factors for major postoperative complications.Conclusions:The POD3/2 CRP was the best marker to exclude anastomotic leakage after laparoscopic gastrectomy for AEG.

Urban Multi-Source Water Supply in China: Variation Tendency, Modeling Methods and Challenges

Urban water resources are the basis for the formation and development of cities and the source of urban water supply. However, with the acceleration of urbanization and the explosion of urban populations, the contradiction between water supply and demand in some areas, especially in big cities, has become increasingly prominent. It is simply not sufficient to rely on local conventional water resources to meet urban water demand, and a single source water supply mode has a higher vulnerability, resulting in greater safety risks in urban or regional water supply systems. Therefore, giving full play to the water supply capacity and carrying out multi-source water supplies are necessary and urgent. This paper gives an overview of the optimal allocation of multi-source for urban water supply concerning variation tendency, modeling methods and facing challenges. Based on the variation tendency of water consumption and water supply pattern in China, Tianjin is taken as a typical city for systematically outlining water supply changes and cause analysis. Subsequently, the modeling methods for proposing the optimal allocation scheme are summarized, which are composed of defining the topological relation, constructing the mathematical model and seeking the optimal solution. Ultimately, the current and emerging challenges are discussed including emergency operation of multi-source water supply and joint operation of water quality and quantity. These summaries and prospects provide a valuable reference for giving full play to the multi-source water supply capacity and carrying out relevant research so as to propose the optimal allocation scheme in urban multi-source water supply systems.