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Objective: The fatigue strength of a new type of vertical retort under the cyclic load of heat engine was studied, especially the residual fatigue life of the pot body after the crack appeared and the factors affecting the fatigue crack propagation of the germicidal pot. Methods: The mechanical characteristics of retort under sterilization and three kinds of cyclic loads were analyzed by Workbench, the design fatigue life of the retort under three alternating stresses was studied based on the S-N curve. The effect of the initial crack size, pressure and temperature on the stress strength factor and residual fatigue life of the crack retort were studied based on fracture mechanics. Results: The design fatigue life of this type of vertical retort was calculated to be 5×105 times, which meet the design requirements, and has a certain safety margin. Based on the fracture mechanics analysis, the crack size life curve of the sterilization retort was obtained, and the residual life of the sterilization retort with defects was predicted, which had certain innovation. Conclusion: Attention should be paid to the occurrence and propagation of cracks in the pot during use. The strength analysis and life prediction analysis of crack defects in the sterilization retort can be carried out according to the method proposed in this paper and experiment.

Objective: In order to explore the distribution law of the flow channel of polylactic acid in different screw contact states of the counter-rotating twin-screw extruder. Methods: Partially meshing screw and non-meshing screw were established by Solidworks software. Numerical sim-ulation was carried out using POLYFLOW fluid simulation software. The pressure field, shear rate field and viscosity field of polylactic acid fluid under different contact states of three screws were compared. Results: The counter-rotating twin-screw extruder in the partially meshed state has better pressure-building ability and dispersing and mixing ability for polylactic acid. Conclusion: The extrusion effect of polylactic acid in the partially meshed state is better than the other two screw contact states.

Objective: To explore the influence of different screw configurations of intermeshing co-rotating twin -screw extruder on the flow field and improve the material properties of PLA. Methods: The geometric model of double threaded element was established by using Solidworks software, and the numerical simulation was carried out in Polyflow. The post-processing analysis of the simulation results was carried out with the help of Fieldview software. The shear rate field, pressure field, velocity field, viscosity field and the residence time distribution RTD were compared to obtain the influence of screw groove depth on the flow field. Results: When the center distance was the same, the depth of the screw groove was changed by changing the ratio of the outer diameter to the inner diameter of the threaded element, physical fields and mixing performance had great differences in the flow field of intermeshing co-rotating twin-screw extruder under the same process conditions. Compared with configuration 2, configuration 1 had stronger shear effect, but configuration 2 had better pressure building ability. In the extrusion process, configuration 2 had good axial mixing ability but poor self-cleaning ability, while configuration 1 had poor axial mixing ability and good self-cleaning ability. Conclusion: The change in screw groove depth has certain effects and rules on the mixing performance of the flow field, which can effectively guide the design of threaded element for twin-screw extruder.

During the past decades, extensive nitrogen fertilization and acid deposition have greatly contributed to soil acidification in agroecosystems. Liming, the addition of calcium- and magnesium-rich material to soil, is an effective management strategy used to improve fertility and productivity of agricultural soils degraded by acidification. Nitrification plays a central role in nitrogen (N) availability in agroecosystems and contributes to soil acidification. However, little is known regarding the effects of liming on this process and microbial populations that drive it. Here, we investigated population dynamics and activity of ammonia oxidizers in response to a 2-year liming field trial in acidic soils received long-term fertilization with chemical N fertilizers and short-term lime amendment in microcosm incubations. Our results showed that activity, abundance and population structure of both ammonia-oxidizing archaea (AOA) and bacteria (AOB) were sensitive to liming in fertilized acidic soils. AOB abundance and potential nitrification rates increased in field plots subjected to liming, whereas the opposite was observed for AOA. In microcosm incubations, AOA abundance increased progressively over 60 days, namely under low CaO levels, whereas AOB abundance was greatly stimulated only during the first week under high CaO levels. 13CO2-SIP-DNA experiments further supported that AOA were the most active ammonia oxidizers in fertilized field soils. However, in N-fertilized soils freshly amended with CaO, only autotrophic growth of AOB was observed after seven days, but not after 30 days when growth of AOA was observed. Taken together, our results indicated that both AOA and AOB play a role in nitrification following liming in fertilized acidic soils, likely through selection of better adapted clades of organisms. Although AOA were likely the main drivers of nitrification in these soils in the long-term, liming stimulated AOB activity in the short-term.

The use of microbial inoculant is a promising strategy to improve plant health, but their efficiency often faces challenges due to difficulties in successful microbial colonization in soil environments. To this end, the application of biostimulation products derived from microbes is expected to resolve these barriers via direct interactions with plants or soil pathogens. However, their effectiveness and mechanisms for promoting plant growth and disease resistance remain elusive. In this study, we showed that root irrigation with the extracts of Streptomyces ahygroscopicus strain 769 (S769) solid fermentation products significantly reduced watermelon Fusarium wilt disease incidence by 30% and increased the plant biomass by 150% at a fruiting stage in a continuous cropping field. S769 treatment led to substantial changes in both bacterial and fungal community compositions, and induced a highly interconnected microbial association network in the rhizosphere. The root transcriptome analysis further suggested that S769 treatment significantly improved the expression of the MAPK signalling pathway, plant hormone signal transduction and plant–pathogen interactions, particular those genes related to PR‐1 and ethylene, as well as genes associated with auxin production and reception. Together, our study provides mechanistic and empirical evidences for the biostimulation products benefiting plant health through coordinating plant and rhizosphere microbiome interaction. [ABSTRACT FROM AUTHOR]

Three new triterpenoid glycosides, 2α,3α,23,24-tetrahydroxyurs-12,19- dien-oic acid 28-O-β- D -glucopyranoside (1), 2α,3β,23,24-tetrahydroxyurs-12, 19(29) -dien-28-oic acid 28-O-β- D -glucopyranoside (2), and 2α,3β,23,24-tetrahydroxyurs-12, 18-dien-28-oic acid 28-O-β- D -glucopyranoside (3) were isolated from Aronia melanocarpa (Michx.) Elliott. Their structures were elucidated by extensive spectroscopic methods. All the isolated compounds displayed moderate inhibitory activity against nitric oxide production in macrophages. [ABSTRACT FROM AUTHOR]

Further investigation on the roots of Aconitum weixiense led to the isolation of two new bis-diterpenoid alkaloids, named as weisaconitines E and F (1–2), which were elucidated by IR, HR-ESI-MS, 1D- and 2D-NMR analyses. Their structures are characterized as denudatine-atisine-type bis-diterpenoid alkaloids. [ABSTRACT FROM AUTHOR]