Temporal rich club phenomenon and its formation mechanisms.

The temporal rich club (TRC) phenomenon is widespread in real systems, forming a tight and continuous collection of the prominent nodes that control the system. However, there is still a lack of sufficient understanding of the mechanisms of TRC formation. Here we use the international N-nutrient trade network as an example of an in-depth identification, analysis, and modeling of its TRC phenomenon. The system exhibits a statistically significant TRC phenomenon, with eight economies forming the cornerstone club. Our analysis reveals that node degree is the most influential factor in TRC formation compared to other variables. The mathematical evolution models we constructed propose that the TRC in the N-nutrient trade network arises from the coexistence of degree-homophily and path-dependence mechanisms. By comprehending these mechanisms, we introduce a different perspective on TRC formation. Although our analysis is limited to the international trade system, the methodology can be extended to analyze the mechanisms underlying TRC emergence in other systems.

Microstructural Characteristics of the Weighted and Directed International Crop Trade Networks.

With increasing global demand for food, international food trade is playing a critical role in balancing the food supply and demand across different regions. Here, using trade datasets of four crops that provide more than 50% of the calories consumed globally, we constructed four international crop trade networks (iCTNs). We observed the increasing globalization in the international crop trade and different trade patterns in different iCTNs. The distributions of node degrees deviate from power laws, and the distributions of link weights follow power laws. We also found that the in-degree is positively correlated with the out-degree, but negatively correlated with the clustering coefficient. This indicates that the numbers of trade partners affect the tendency of economies to form clusters. In addition, each iCTN exhibits a unique topology which is different from the whole food network studied by many researchers. Our analysis on the microstructural characteristics of different iCTNs provides highly valuable insights into distinctive features of specific crop trades and has potential implications for model construction and food security.

[Preparation and NH4+-N Removal Performance of a Novel Filter Substrate Made from Sludges].

A novel absorbent was prepared by high-temperature calcination using waterworks terminal aluminum coagulation sludge as a raw material. This study discussed ammonia nitrogen adsorption performance of the adsorbent by static adsorption test, mainly investigated the influences of different initial pH, contact time and temperatures on the ammonia adsorption effect, and also analyzed the adsorption isotherms, kinetic and thermodynamic properties of adsorbent on the ammonia nitrogen. Experimental results showed that the adsorbent had a better effect for ammonia removal under neutral conditions; the adsorption process was basically balanced within 6 h, and it followed the pseudo second-order model. Langmuir adsorption model could be better fitted for the adsorption of ammonia adsorbent; the thermodynamic parameters indicated that the adsorption process of ceramic adsorbents on NH4+-N was a kind of spontaneous, endothermic reaction (ΔGθ <0, ΔHθ >0), and it was found to be a physical adsorption based on the average adsorption energy. Thus, treating ammonia wastewater by coagulation sludge has a good prospect.

[Effects of UV radiation on the aggregation performance of small molecular organic acids].

This study systematically investigated the effects of UV radiation on the aggregation of small molecular aliphatic carboxylic acids and phenolic acids by jar test. Experimental results show that solution pH has little effect on the coagulation of small molecular aliphatic carboxylic acids including citric acid, oxalic acid, tartaric acid, and succinic acid. For the solutions pretreated with UV light, the removal rates of the selected aliphatic carboxylic acids in coagulation are higher than that without UV radiation. Further study shows that photochemical reactions occur during UV radiation which decreases the negative charge in aliphatic carboxylic acids, and thereby increases their aggregation properties. Different from aliphatic carboxylic acids, phenol, salicylic acid, and benzoic acid have poor coagulation properties, and UV radiation does not have notable effects on their aggregation in the coagulation process. The coagulation performance of tannic acid is better than the other phenolic acids. At pH = 6, its removal rate is above 90%, which may be contributed to the aliphatic carboxylic acid structure in its molecular. Meanwhile, the large molecular of tannic acid is also easier to be adsorbed by the hydrolysis products of PAC1.