Bacterial wilt suppressive composts: Significance of rhizosphere microbiome.

Composts are often suppressive to several plant diseases, including the devastating bacterial wilt caused by Ralstonia solanacearum. However, the underlying mechanisms are still unclear. Herein, we carried out an experiment with 38 composts collected from different factories in China to study the interlinking among bacterial wilt suppression, the physicochemical properties and bacterial community of the compost, and bacterial community in the rhizosphere of tomato fertilized by compost. Totally 26 composts were suppressive to bacterial wilt, while six composts stimulated the disease. The control efficiency was neither correlated with physicochemical properties (TC, TN, P and K, pH or GI) nor bacterial community of compost, but with rhizosphere bacterial community (r = 0.17, p = 0.016). The control efficiency was also positive correlated with taxa (Rhizobium, Aeromicrobium) known suppressive to R. solanacearum. The mushroom spent or cow manure, from which the two composts were 100% and 77% in control efficiencies against bacterial wilt respectively were subject to a pilot-scale composting reaction. The reproduced composts from mushroom spent or cow manure were only 57% and 23% effective on the control of bacterial wilt, respectively. The analysis of bacterial communities revealed that the relative abundances of R. solanacearum were 28.4% for the control, but only 7.8%-7.9% for compost fertilized tomatoes. The compost from mushroom spent also exerted a strong effect on rhizosphere bacterial community. Taken together, most composts were suppressive to bacterial wilt possibly also by modifying rhizosphere bacterial community towards inhibiting the colonization of R. solanacearum and selecting for beneficial genera of Proteobacteria, Bacteroidetes and Actinobacteria.

Mechanical Properties of Polyurethane Mixture and Load Response Behaviour of Polyurethane Composite Pavement.

Finite element numerical simulation calculation of pavement structure load response is widely applied; however, there is still a lack of research on the polyurethane (PU) mixture composite pavement load response. The mechanical characteristics of PU mixture composite pavement are not well understood, and there is a lack of research on typical pavement structures of PU mixtures, which limits their application in pavement structures. Therefore, herein, the mechanical properties of PU mixtures are analysed using the dynamic modulus test, uniaxial penetration test, and fatigue test. Further, the finite element theory calculation method is used to realize the load response calculation of orthogonal design composite pavement structure. The results show that PU mixtures exhibit more obvious elastic characteristics and have good shear resistance, fatigue stability, and temperature stability, and can be used as shear and anti-fatigue layers. The structure of '4 cm SMA-13 + 5 cm PUM-20 + 6 cm PUM-25 + semi-rigid base' is recommended for the PU mixture composite structure. In comparison to typical asphalt pavement, the analysis shows that except for shear stress, temperature has little effect on the load response of PU composite pavement structures, while high temperatures lead to a significant increase in the load response of typical asphalt pavement structures. The PU composite pavement can bear greater loads and has a reduced thickness of its surface layer by about 3 cm in comparison to conventional pavement. The results of this study provide theoretical support for the design of PU mixture pavement structures and promote the popularization and application of PU mixture pavement.

Effect of curing regime on the immobilization of municipal solid waste incineration fly ash in sustainable cement mortar.

Stabilizing/solidificating municipal solid waste incineration fly ash (MIFA) with cement is a common strategy, and it is critical to study the high-value utilization of MIFA in ordinary Portland cement (OPC) components. With this aim, binary-binding-system mortar was produced by partially replacing OPC (∼50%) with MIFA, and the effects of different curing regimes (steam curing and carbonation curing) on the properties of the cement mortar were studied. The results showed that the setting time of the cement paste was shorten with the increase of MIFA content, and steam curing accelerated the hardening of the mixture. Although the incorporation of MIFA reduced the strength of the mortar, compared to conventional curing method, steam curing and carbonation curing increased the 3-d strength of the mortar. For high-volume MIFA mortars, the CO2-cured samples had the highest long-term strength and lowest permeability. The incorporation of MIFA increased the initial porosity of the mortar, thereby significantly increasing the carbonation degree and crystallinity of the reaction product - CaCO3. Steam curing also further narrowed the difference in the hydration degree between MIFA-modified sample and plain paste, which may be due to the enhanced hydraulic reactivity of MIFA at high temperatures. Although the incorporation of MIFA increased the porosity of the mortar, this waste-derived SCM refined the bulk pore structure and decreased the interconnected porosity. Additionally, the heavy metal leaching contents of MIFA-modified mortars were all below 1%, which meet the requirements of Chinese standards. Compared with standard curing, steam curing and carbonation curing made the early-age and long-term performance of MIFA-modified mortar better, which can promote the efficient application of MIFA in OPC products.

A multi-stage heuristic method for service caching and task offloading to improve the cooperation between edge and cloud computing.

Edge-cloud computing has attracted increasing attention recently due to its efficiency on providing services for not only delay-sensitive applications but also resource-intensive requests, by combining low-latency edge resources and abundant cloud resources. A carefully designed strategy of service caching and task offloading helps to improve the user satisfaction and the resource efficiency. Thus, in this article, we focus on joint service caching and task offloading problem in edge-cloud computing environments, to improve the cooperation between edge and cloud resources. First, we formulated the problem into a mix-integer nonlinear programming, which is proofed as NP-hard. Then, we proposed a three-stage heuristic method for solving the problem in polynomial time. In the first stages, our method tried to make full use of abundant cloud resources by pre-offloading as many tasks as possible to the cloud. Our method aimed at making full use of low-latency edge resources by offloading remaining tasks and caching corresponding services on edge resources. In the last stage, our method focused on improving the performance of tasks offloaded to the cloud, by re-offloading some tasks from cloud resources to edge resources. The performance of our method was evaluated by extensive simulated experiments. The results show that our method has up to 155%, 56.1%, and 155% better performance in user satisfaction, resource efficiency, and processing efficiency, respectively, compared with several classical and state-of-the-art task scheduling methods.

Experimental study on full-volume slag alkali-activated mortars: Air-cooled blast furnace slag versus machine-made sand as fine aggregates.

As the industrial waste from blast furnace ironmaking, air-cooled blast furnace slag (ACBFS) puts a lot of pressure on the environment. It is becoming more and more urgent to deal with the increasing ACBFS. In this study, the concept of "full-volume slag alkali-activated mortars (FSAM)" is proposed using ground granulated water-cooled blast furnace slag (GGBS) as aluminosilicate material and ACBFS to replace machine-made sand, aiming to solve the current situation of increasing scarcity of natural resources. The characteristics of ACBFS are investigated, and its stability and heavy metal leaching all meet the requirements as a building material. The results show that the flowability and mechanical properties of FSAM are significantly enhanced with the substitution rate of ACBFS increases. Meanwhile, the incorporation of ACBFS is also beneficial to improve the compactness of the microstructure of the mortar, thereby improving the impermeability (Water, ion and gas) of FSAM. In addition, the specimen mixed with ACBFS showed good high temperature resistance due to the porous feature of the aggregate. Furthermore, using a small amount of limestone powder to replace GGBS can slightly improve the performance of FSAM. Therefore, ACBFS is recommended to be used in FSAM, which meets safety, cost and environmental benefits.