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Alfalfa is a perennial herbaceous forage legume that is significantly and adversely affected by monocropping. Crop rotation is the most effective measure to overcome continuous cropping obstacles. However, the mechanisms of how bacterial communities are affected and the potential links between these effects and cropping systems remain poorly understood. Based on a long-term field experiments with continuous alfalfa and forage crops with alfalfa rotation in the black soil region of the western Songnen Plain in Northeast China, the alterations in soil bacterial community structure using high-throughput sequencing of the 16S rRNA gene and soil chemical properties and enzyme activities were analyzed. The alfalfa–forage oats–silage maize–alfalfa and alfalfa–silage maize–forage oats–alfalfa system significantly increase the levels of total phosphorus and available phosphorus, and promote the activities of acid phosphatase, β-glucosidase, leucine aminopeptidase, and N-acetyl-β-glucosaminidase in comparison to continuous alfalfa. While alfalfa crop rotation did not affect the α-diversity of soil bacteria, it significantly altered the bacterial community composition and structure. Some key taxa are significantly enriched in the crop rotation system soils, including Bacillus, Sphingobium, Paenibacillus, Hydrogenispora, Rubrobacter, Haliangium, and Rubellimicrobium. Additionally, crop rotation with alfalfa increased the stability and complexity of the soil bacterial co-occurrence network. Based on our findings, we recommend promoting the alfalfa–forage oats–silage maize–alfalfa and alfalfa–silage maize–forage oats–alfalfa rotation systems as ideal practices for overcoming the challenges associated with continuous cropping of alfalfa. These systems not only enhance soil nutrient content and enzyme activities but also foster a beneficial microbial community, ultimately improving soil functionality and crop performance. [ABSTRACT FROM AUTHOR]

Particle image velocimetry (PIV) is a widely used experimental technique in ocean engineering, for instance, to study the vortex fields near marine risers and the wake fields behind wind turbines or ship propellers. However, the flow fields measured using PIV in water tanks or wind tunnels always have low resolution; hence, it is difficult to accurately reveal the mechanics behind the complex phenomena sometimes observed. In this paper, physics-informed neural networks (PINNs), which introduce the Navier–Stokes equations or the continuity equation into the loss function during training to reconstruct a flow field with high resolution, are investigated. The accuracy is compared with the cubic spline interpolation method and a classic neural network in a case study of reconstructing a two-dimensional flow field around a cylinder, which is obtained through direct numerical simulation. Finally, the validated PINN method is applied to reconstruct a flow field measured using PIV and shows good performance. [ABSTRACT FROM AUTHOR]

An experimental investigation on the vortex/wake-induced force of double unequal-diameter cylinders in tandem was performed. In the experiment, the upstream-to-downstream cylinder diameter ratio was 1.569, and the gap spacing ratio between the cylinder models ranged from 3 to 8. Under uniform flow with Reynolds number up to 11 328, the strains caused by the vortex/wake-induced vibrations were measured for the double flexible cylinders. Based on the measured strains, the displacements were reconstructed with the mode superposition method. Then, the vortex/wake-induced forces were obtained inversely. Subsequently, the time-varying excitation and added mass coefficients were identified by the forgetting factor least squares method. The results show that the wake-induced force coefficient and excitation coefficient of the downstream cylinder are smaller than those of the single cylinder, while the added mass coefficient becomes larger. In addition, the downstream cylinder under frequency capture can absorb a higher proportion of energy from the wake to excite larger vibration amplitudes, especially in the in-line direction. [ABSTRACT FROM AUTHOR]

A frequency capture phenomenon in which the dominant response frequency of the downstream cylinder is the same as that of the upstream cylinder despite the differences in their physical characteristics was recently experimentally identified. The mechanism of this phenomenon is investigated by flow around two cylinders with unequal diameters undergoing flow-induced vibrations (FIV) using the open-source code OpenFOAM. Two FIV systems, a large stationary/vibrating upstream cylinder and vibrating downstream cylinder, are used for the simulation. The cylinders are free to vibrate in both the in-line and cross-flow directions. The forgetting factor least squares algorithm is applied for the time-varying excitation mechanism analysis. Simulation results show that the response of the downstream cylinder has a larger amplitude and contains multi-frequency components than the vortex-induced vibration of an isolated cylinder, making its trajectory more complicated. Simulations confirm that the frequency capture phenomenon is induced by the action of the upstream shedding vortex on the downstream cylinder. The energy transfers from vorticity to the structure when the frequency capture phenomenon occurs. The response of the downstream cylinder comprises a significant component of the vortex shedding frequency of the upstream cylinder. [ABSTRACT FROM AUTHOR]

Unguided exploitation has impaired the sustainability of natural resources of agronomic non-wood forest plants from understory boglands in boreal forests. The extreme consequences of plant–soil interplay on medicinal plant communities under continuous interruptions need to be understood to implement strategies which can cope with possible ecological degradation. In this study, co-existing Ledum palustre and Vaccinium uliginosum communities were investigated after a four-year interruption of continuous removal of dominant species in stands at Xing'an Mountain. Nitrogen (N) availability was assessed by above-ground biomass and N content in nondominant plants and the biophysiological properties of rhizosphere soil. The removal treatment promoted soil mineral and organic N contents, but also reduced abundances of the soil communities of Rozellomycota phylum (by 82.76%), ericoid mycorrhiza of Meliniomyces varia (by 81.60%) and Phialocephala fort (by 69.54%). Vaccinium uliginosum overcame L. palustre through higher N utilization (biomass/%N) although the latter had higher abundances of soil Odiodendron maius and P. fort. The microbial community attributes accounted for a large proportion of N availability following the removal of dominance. In conclusion, our study demonstrates that understory agronomic plants in northern boglands should no longer be under continuous exploitation. Strategies should be considered to improve the promotion of N uptake by managing local soil microbial communities. [ABSTRACT FROM AUTHOR]

Potato onion has facilitating effect on tomato seedlings; however, the mechanisms underlying the facilitating effect remain unknown. Here, we examined the effects of potato onion leaf volatiles and leachates on tomato seedling growth, and performed a transcriptomic comparison of two potato onion cultivars with different facilitating potentials ('Suihua': higher facilitating potential; 'Qitaihe': lower facilitating potential). Potato onion leaf volatiles and leachates decreased the stem length, but increased the shoot dry matter of tomato seedlings. Transcriptomic analysis showed that 640 genes were differentially expressed (DEGs) between 'Suihua' and 'Qitaihe.' DEGs related to photosynthesis, energy metabolism, and hormone metabolism were higher expressed in 'Suihua' compared to that in 'Qitaihe,' whereas genes related to phenylpropanoid metabolism and disease resistance were lower expressed. Pathway analysis showed the DEGs mainly participated in Metabolism, Biosynthesis of secondary metabolites and Plant hormone signal transduction. [ABSTRACT FROM AUTHOR]

Helical strakes are widely used to suppress vortex-induced vibration (VIV) in ocean engineering. However, the VIV response and suppression efficiency of the straked pipe are unclear under the recently discovered bidirectionally sheared flow field. Experiments on vortex-induced vibration for a flexible pipe with three kinds of helical strakes were carried out in an ocean basin. The bare pipe model was 28.41 mm in diameter and 7.64 m in length. Three kinds of helical strakes with different pitch/height (17. 5 D / 0. 15 D , 17. 5 D / 0. 25 D ,and 17. 5 D / 0. 35 D) were applied. The test was performed on a rotating test rig to simulate bidirectionally sheared flow conditions. Fiber Bragg Grating (FBG) strain sensors were arranged along the test pipe to measure bending strains, and the modal analysis approach was used to determine the VIV response. The reduced velocities based on the tested first natural frequency of the bare pipe in water reached 30.79. The cross-flow and in-line VIV amplitudes, VIV suppression efficiency, and fatigue damage are presented in this article. The results showed that the helical strakes can suppress bidirectionally sheared flow-induced VIV significantly at a high reduced velocity regime with fatigue damage suppression efficiency over 99% in the CF and IL directions, but cannot suppress the in-line initial displacement, which was also found in previous studies as a drawback of helical strakes. • An experiment of a straked flexible pipe that was 28.41 mm in diameter and 269 diameters in length under bidirectionally sheared flow was conducted. • The helical strakes significantly suppress VIV in the high reduced velocity regime. The maximum suppression efficiency reached 94 % and 87% in the CF and IL directions, respectively. • The helical strake was also effective against VIV fatigue damage. The maximum fatigue suppression efficiency reaches 99% in the CF and IL directions, respectively. • The helical strake cannot suppress the initial IL response in bidirectionally sheared flow induced by mean drag. [ABSTRACT FROM AUTHOR]

Cytidine triphosphate synthase (CTPS) forms filamentous structures termed cytoophidia in numerous types of cell. Toosendanin (TSN) is a tetracyclic triterpenoid and induces CTPS to form cytoophidia in MKN45 cells. However, the effects of CTPS cytoophidia on the proliferation and apoptosis of human gastric cancer cells remain poorly understood. In the present study, CTPS-overexpression and R294D-CTPS mutant vectors were generated to assess the effect of CTPS cytoophidia on the proliferation and apoptosis of gastric cancer MKN45 cells. Formation of CTPS cytoophidia significantly inhibited MKN45 cell proliferation (evaluated using EdU incorporation assay), significantly blocked the cell cycle in G1 phase (assessed using flow cytometry) and significantly decreased mRNA and protein expression levels of cyclin D1 (assessed by reverse transcription-quantitative PCR and western blotting, respectively). Furthermore, the number of apoptotic bodies and apoptosis rate were markedly elevated and mitochondrial membrane potential was markedly decreased. Moreover, mRNA and protein expression levels of Bax increased and Bcl-2 decreased markedly in MKN45 cells following transfection with the CTPS-overexpression vector. The proliferation rate increased, percentage of G1/G0-phase cells decreased and apoptosis was attenuated in cells transfected with the R294D-CTPS mutant vector and this mutation did not lead to formation of cytoophidia. The results of the present study suggested that formation of CTPS cytoophidia inhibited proliferation and promoted apoptosis in MKN45 cells. These results may provide insights into the role of CTPS cytoophidia in cancer cell proliferation and apoptosis. [ABSTRACT FROM AUTHOR]

• Streptomyces sp. FXP04 inhibited the mycelial growth of P. infestans in vitro. • Streptomyces sp. FXP04 reduced late blight damage on potato plants in pot trials. • Streptomyces sp. FXP04 secretes Piericidin A, a polyketide secondary metabolite. • Piericidin A inhibits the mycelial growth of P. infestans in vitro. Potato late blight, caused by the oomycete Phytophthora infestans , is a devastating disease of potato globally. Antagonistic microorganisms have been used as biological control agents to inhibit P. infestans and reduce the use of synthetic fungicides. In the present study, a bacterial isolate (FXP04) was obtained from the rhizosphere soil of potato plants and demonstrated to significantly inhibit the mycelial growth of P. infestans in vitro. In a pot experiment, application of FXP04 to potato tubers prior to planting and to the soil after planting decreased both disease incidence and the disease index of potato late blight. Analysis of the 16S rDNA sequence of FXP04 indicated that the strain belonged to the genus, Streptomyces, and thus the strain was named Streptomyces sp. FXP04. The genome of Streptomyces sp. FXP04 was sequenced to determine the presence of gene clusters encoding secondary metabolites. AntiSMASH software analysis identified 15 gene clusters responsible for the biosynthesis of secondary metabolites, including the antimicrobial compound, Piericidin A. Metabolomic analysis of the fermentation broth of Streptomyces sp. FXP04 identified the presence of Piericidin A. Additional experiments indicated that Piericidin A inhibited the mycelial growth of P. infestans. The results of our study indicate that Streptomyces sp. FXP04 represents a potential biocontrol agent that could be used to control potato late blight. Furthermore, Piericidin A may represent the antimicrobial secondary metabolite responsible for the biological control activity of Streptomyces sp. FXP04. [ABSTRACT FROM AUTHOR]