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• Auxetic foam is used in seismic metamaterials that attenuate surface waves for the first time. • A quasi-zero bandgap from 0 to 16.42 Hz is opened via the inverse dispersion effect. • Vibration modes, distribution of Mises stress and storage density diagram of energy are calculated and analyzed. • Time domain analysis and scaled-down experiment are carried out. Auxetic materials with negative Poisson's ratio (PR) exhibit superior mechanical properties with regard to energy absorption, while their potential for surface wave shielding is only in its beginnings. To attenuate surface waves in ultra-low frequencies (the starting frequency close to 0 Hz), which is the main scope of concern in seismic protection, this paper presents a novel type of seismic metamaterial (SM) with square pillars embedded as vibrators that is filled by auxetic foam. The designed SM is comprised of three commonly used construction materials, i.e., soil, concrete and auxetic foam. Combining the dispersive analysis and sound cone method, an ultra-low-frequency bandgap from 0 to 16.42 Hz is opened via the tensile resonance of the auxetic foam and the inverse dispersion effect. Furthermore, the parametric analysis further shows that filling material with a low Poisson ratio and low mass density is more favorable to widening the first complete bandgap (FCB), which means that foam is the ideal filling material for SM. The transmission spectra of the corresponding finite samples coincide well with the bandgap calculations. And the dynamic response of a scaled-down setup with a characteristic size of 1/10 of the original metamaterial is experimentally tested to validate the effectiveness of our study. We expect that this study prompts the engineering application of auxetic materials and ordinary building materials in seismic wave shielding at deep sub-wavelength frequencies. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • A meter-scale ultra-low frequency wide-bandgap seismic metamaterial for Lamb waves is proposed for the first time, and the bandgap can cover the 2 Hz seismic peak spectrum. • Band structures, vibration modes and transmission spectrum of the seismic metamaterial are calculated and analyzed. • The influences of geometrical parameters, material parameters value on the bandgap width and location are discussed. • The structure is optimized, and the effects of the different forms of matrix on the attenuation degree of the transmission spectrum is discussed. Seismic metamaterials (SMs) have attracted the attention of many researchers in the field of damping and elastic wave isolation because of their bandgap properties, i.e., attenuating elastic waves in the range of bandgaps. However, the dimension of these SMs often reaches the 10-meter scale, which impedes practical engineering application. To break through this bottleneck and achieve a smaller scale, a meter-scale novel SM composed of steel and rubber is proposed for attenuating ultra-low frequency seismic Lamb waves. Firstly, the finite element method is used to analyze the band structure of SMs and calculate the bandgaps. To explain the mechanism of bandgap, the vibration modes of the waves at the bandgap boundary frequency are further analyzed. Subsequently, the transmission spectrum of Lamb waves incidents on the finite SMs system is analyzed to prove the authenticity of the bandgaps. Finally, parameter analyses including the geometric variables, material properties, equivalent mass density, and structural matrix forms with identical equivalent mass density are investigated numerically. The results show that Lamb waves in the range of 0–20 Hz are significantly attenuated by SMs, and the aforementioned parameters are significant factors affecting the bandgap properties and transmission properties. The proposed SM has a smaller size while maintaining some wide bandgaps at 0–20 Hz for ultra-low frequencies. It is worth noting that the 2 Hz seismic peak spectrum causing the destruction of building structures is covered effectively. [ABSTRACT FROM AUTHOR]

Phytoalexins play a crucial role in plant immunity. However, the mechanism of how phytoalexin is primed by beneficial microorganisms against broad‐spectrum pathogens remains elusive. This study showed that Bacillus cereus AR156 could trigger ISR against broad‐spectrum disease. RNA‐sequencing and camalexin content assays showed that AR156‐triggered ISR can prime the accumulation of camalexin synthesis and secretion‐related genes. Moreover, it was found that AR156‐triggered ISR elevates camalexin accumulation by increasing the expression of camalexin synthesis genes upon pathogen infection. We observed that the priming of camalexin accumulation by AR156 was abolished in cyp71a13 and pad3 mutants. Further investigations reveal that in the wrky33 mutant, the ability of AR156 to prime camalexin accumulation is abolished, and the mediated ISR against the three pathogens is significantly compromised. Furthermore, PEN3 and PDR12, acting as camalexin transporters, participate in AR156‐induced ISR against broad‐spectrum pathogens differently. In addition, salicylic acid and JA/ET signalling pathways participate in AR156‐primed camalexin synthesis to resist pathogens in different forms depending on the pathogen. In summary, B. cereus AR156 triggers ISR against Botrytis cinerea, Pst DC3000 and Phytophthora capsici by priming camalexin synthesis. Our study provides deeper insights into the significant role of camalexin for AR156‐induced ISR against broad‐spectrum pathogens. Summary statement: Beneficial rhizobacterium AR156 triggered ISR by enhancing camalexin accumulation in Arabidopsis, with WRKY33 acting as a positive regulator. PEN3 and PDR12 are involved in AR156‐induced ISR. Salicylic acid and JA/ET signalling pathways participate in AR156‐primed camalexin synthesis to resist various pathogens. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bacillus amyloliquefaciens HSSN09 with antagonistic effect on FON was isolated. • B. amyloliquefaciens HSSN09 could effectively control watermelon Fusarium wilt and promote the growth of watermelon seedlings. • Tacrolimus has a very obvious antifungal effect and can be used to control watermelon Fusarium wilt. • Tacrolimus was also able to stimulate the growth of watermelon seedlings. • Tacrolimus or its analogs may play a role as a pleiotropic factor in B. amyloliquefaciens HSSN09 biological control. Watermelon Fusarium wilt caused by Fusarium oxysporum f. sp. niveum (FON) is one of the most devastating diseases in watermelon production. Biological control approaches are efficient and environmentally-friendly, thus have aroused broad interest. However, only a few biocontrol factors/molecules have been characterized due to varied genomes and diversified secreted secondary metabolites of biocontrol microorganisms. We report the screen and identification of a Bacillus amyloliquefaciens strain HSSN09 with high antagonism to FON and watermelon growth promotion capacity. B. amyloliquefaciens HSSN09 and its secondary metabolites showed inhibition on FON mycelial growth, spore formation and spore germination. Metabolomes of the highly antagonistic strain B. amyloliquefaciens HSSN09, medium antagonistic strain B. amyloliquefaciens FGW53, weakly antagonistic strain B. subtilis JC03 and non-antagonistic strain B. cereus FGW109 were compared with LC-MS/MS. By antagonistic assay, tacrolimus was screened out among the 531 molecules that appeared in the sequencing results of HSSN09 metabolome but not in that of the non-antagonistic strain without significant inhibition on the growth of FON. Among the four tested Bacillus strains, tacrolimus analogue was only observed in the supernatant of HSSN09 by HPLC and MALDI-TOF-MS. We further confirmed the ability of tacrolimus to suppress FON and promote watermelon seedling growth. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Poisson's ratio is completely opposite when the metamaterial stress is kept constant. • Poisson's ratio can exceed ± 1 , realize out-of-plane deformation rate exceeds in-plane. • Adjustable resistance to the ball passing through the tubular structure. • Parametric results improve its stress, Poisson's ratio, deformation mode and energy absorption. In this study, a three-dimensional compression-torsion coupled negative Poisson structure was designed by combining the perforated plate with the inclined rod out of the plane. This structure can realize the selection of the positive and negative Poisson's ratio of the three-dimensional structure by changing the direction of the inclined rod. The absolute value of the Poisson's ratio of the two structures is close to the same but the positive and negative are opposite. Both structures maintain close to the same stress–strain curve. This structural characteristic can realize the selection of an ideal Poisson's ratio without changing the mechanical properties of the structure. Two 3D compression-torsion coupling structures were printed using metal 3D printing technology, and compression tests were carried out in the axial and transverse directions. Then, parametric analysis was carried out under axial compression, including energy absorption and specific energy absorption analyses. The results show that the experimental and finite element results are in good agreement and the finite element simulation is accurate. The Poisson's ratio of this negative Poisson's ratio metamaterial is selectable under both axial and lateral pressure conditions, so the structure has the excellent characteristics of selectable Poisson's ratio in three mutually perpendicular axes. The results show that the absolute value of Poisson's ratio exceeds 1 when the structure is under lateral compression, which indicates that the lateral deformation rate of the structure is greater than the axial deformation rate under this compression form. Finally, two tubular structures with different arrangements were designed by using these two structural cells, and the ball passing test was carried out. The results show that different arrangements will cause the balls to experience different resistances when passing through different positions in the tube. Research shows that the structure has potential applications in energy absorption, biomechanical devices, smart actuators, and devices with special requirements for Poisson's ratio. [ABSTRACT FROM AUTHOR]

The beneficial effects of plant growth-promoting rhizobacteria (PGPR) on crop growth and yield have been widely recognized. However, the application of PGPR in traditional planting systems is often restricted due to the concerns about the incompatibility between PGPR and chemical agricultural inputs. The aim of this study is to test whether the application of PGPR has a beneficial effect on the productivity and sustainability of the green planting system, where the use of low-toxic chemical pesticides and proper amount of chemical fertilizer is allowed. In the current study, field trials of four agriculture systems: green agriculture system, green agriculture system supplemented with beneficial microorganism consortium, organic agriculture system supplemented with the consortium and the control system, were carried out with white, yellow and purple flesh sweet potato varieties. The application of PGPR increased the plant growth and suppressed the stem nematode disease in green system. As a consequence, PGPR increased the yield by 26.44% and raised the farmers' projected returns in green system on an average of the two-year assessment. Moreover, PGPR promoted the product nutritive quality by 7.51% in soluble sugar and 14.30% in vitamin C content, and also increased the anthocyanin content of the purple sweet potato by 10.73%. Exogenous PGPR significantly retarded the depletion of soil fertility during the crop cultivation, promoted the soil bacterial diversity and altered the bacteria community structure. PGPR treatment increased the relative abundances of Pseudomonas and Lysobacter in the rhizosphere soil, while reduced the amounts of Erwinia and Ralstonia. The changes of soil nutrient and microbes were correlated with the application of exogenous beneficial bacteria regardless of in organic or green agriculture system. Here, we showed the ability of PGPR to efficiently improve the productivity in green agriculture system under the tested condition, and provided evidence for the feasibility of using exogenous PGPR to achieve agricultural sustainability by constructing a positive feedback in crop-soil-microbe interactions. [Display omitted] • PGPR increased soil micro ecological diversity and remodeled population structure. • PGPR in green agriculture system improved the sustainability of agricultural soil. • Proposed the virtuous cycle of plant-soil-microbe driven by PGPR. • PGPR help to develop a balance between productivity, environment and economics. [ABSTRACT FROM AUTHOR]