Diffusible Factor Research Articles

Diffusible signal factor primes plant immunity against Xanthomonas campestris pv. campestris (Xcc) via JA signaling in Arabidopsis and Brassica oleracea.

Many Gram-negative bacteria use quorum sensing (QS) signal molecules to monitor their local population density and to coordinate their collective behaviors. The diffusible signal factor (DSF) family represents an intriguing type of QS signal to mediate intraspecies and interspecies communication. Recently, accumulating evidence demonstrates the role of DSF in mediating inter-kingdom communication between DSF-producing bacteria and plants. However, the regulatory mechanism of DSF during the Xanthomonas-plant interactions remain unclear. Plants were pretreated with different concentration of DSF and subsequent inoculated with pathogen Xanthomonas campestris pv. campestris (Xcc). Pathogenicity, phynotypic analysis, transcriptome combined with metabolome analysis, genetic analysis and gene expression analysis were used to evaluate the priming effects of DSF on plant disease resistance. We found that the low concentration of DSF could prime plant immunity against Xcc in both Brassica oleracea and Arabidopsis thaliana. Pretreatment with DSF and subsequent pathogen invasion triggered an augmented burst of ROS by DCFH-DA and DAB staining. CAT application could attenuate the level of ROS induced by DSF. The expression of RBOHD and RBOHF were up-regulated and the activities of antioxidases POD increased after DSF treatment followed by Xcc inoculation. Transcriptome combined with metabolome analysis showed that plant hormone jasmonic acid (JA) signaling involved in DSF-primed resistance to Xcc in Arabidopsis. The expression of JA synthesis genes (AOC2, AOS, LOX2, OPR3 and JAR1), transportor gene (JAT1), regulator genes (JAZ1 and MYC2) and responsive genes (VSP2, PDF1.2 and Thi2.1) were up-regulated significantly by DSF upon Xcc challenge. The primed effects were not observed in JA relevant mutant coi1-1 and jar1-1. These results indicated that DSF-primed resistance against Xcc was dependent on the JA pathway. Our findings advanced the understanding of QS signal-mediated communication and provide a new strategy for the control of black rot in Brassica oleracea.

Sensitivity analysis of a physicochemical model of chloride ingress into real concrete structures subjected to long-term exposure to tidal cycles

In marine environments, reinforced concrete structures are exposed to tidal conditions and therefore susceptible to chloride ingress. Reliable models of transport are crucial in order to evaluate the service life of these structures. Unlike engineering models based on Fick's 2nd law and empirical coefficients, this study proposes a model based on a physicochemical description of the transport phenomena and on some assumptions restricting the number of inputs to 9 parameters and the computational costs. This model is validated for a long exposure to tidal cycles (28 years). Then, the sensitivity analysis, based on the Morris method, is performed through 100 simulations of tidal exposure considering different sets of the 9 input parameters. According to the critical times of initiation of corrosion predicted, the most sensitive parameters are the critical chloride concentration and the chloride diffusivity factors. The effects of moisture sorption and chloride binding parameters are moderate after long exposure. Then, the results of the simulations are compared to data of the literature in terms of convection depths and total chloride concentrations at the limit of the convection / diffusion zones. Finally, by quantitative considerations, the analysis goes further, providing analytical relations expressing the convection depth and the associated total chloride concentration as functions of input parameters. These provide physically informed guidelines in using an engineering model based on Fick's 2nd law in order to estimate the critical time of initiation of corrosion.

Contextualizing Mobile Diffusion of the Sub-Saharan Region: Explanatory Analysis of Factors Affecting Mobile Diffusion in Sub-Saharan African countries

The study aims to challenge the prevalent assumption of technological determinism in the field of mobile diffusion research by utilizing a contextualized approach with quantitative variables. It conducted random effects analysis with the data of 40 sub-Saharan African countries from 2000 to 2017. The study finds that what has been generally accepted, as developed countries’ mobile diffusion factors may not have the same dynamics for the sub-Saharan region due to heterogeneity among countries where collectivistic societal cultures reside in values in the region, and feedback loop features of the mobile diffusion process of the sub-Saharan countries.

A hybrid deterministic-diffuse approach to the analysis of vibration transmission across finite junctions

The average vibro-acoustic performance of a junction between two-dimensional structural elements is often quantified by its diffuse vibration reduction index, especially for building structures. Existing prediction methods either assume an infinite junction length or consider non-diffuse transmission. In this work an approach for predicting the diffuse vibration reduction index of finite junctions of arbitrary complexity is developed. First, the mean and (co)variance of the diffuse coupling loss factor of a finite junction are obtained within the hybrid deterministic-statistical energy analysis framework. Dedicated basis functions are proposed to efficiently describe the interface displacements of the diffuse subsystems. Subsequently, the relation between the mean vibration reduction index and the coupling loss factor is established. It is demonstrated that this relation involves both the mean and the variance of the coupling loss factor. Additionally, the relation between the variance of the vibration reduction index and the (co)variances of the coupling loss factors is derived. Finally, the proposed approach is both numerically validated and compared to experimental results for several finite junctions between building elements, which are modelled as plates. For the numerical validation, the results obtained with the proposed approach are compared with those of an ensemble of junctions with the same bare structure but with point masses attached at random locations on the walls and floors. The validations demonstrate that an accurate prediction of the mean and variance of the diffuse vibration reduction index is possible when the uncertainty across the random ensemble is sufficiently large. The comparison to experimental results involves T and X junctions between directly coupled plates. At low and medium frequencies, the experimental data are well captured within the 95% confidence interval of the hybrid model results. At high frequencies, the uncertainty on the hybrid results is very small; such differences with the experimental data are caused by modelling errors.

Integrability Breaking from Backscattering.

We analyze the onset of diffusive hydrodynamics in the one-dimensional hard-rod gas subject to stochastic backscattering. While this perturbation breaks integrability and leads to a crossover from ballistic to diffusive transport, it preserves infinitely many conserved quantities corresponding to even moments of the velocity distribution of the gas. In the limit of small noise, we derive the exact expressions for the diffusion and structure factor matrices, and show that they generically have off diagonal components. We find that the particle density structure factor is non-Gaussian and singular near the origin, with a return probability showing logarithmic deviations from diffusion.

3-Ketoacyl-ACP synthase III FabH1 is essential for branched-chain DSF family signals in Xanthomonas oryzae pv. oryzae

The 3-ketoacyl-ACP synthase III (FabH), a key enzyme for bacteria growth, catalyses the last step of the initiation of bacterial fatty acid synthesis. Rice bacterial blight is caused by the pathogen Xanthomonas oryzae pv. oryzae (Xoo), which is widely studied as a model bacterium. Bioinformatics analysis showed that the X. oryzae pv. oryzae PXO99A genome encodes three FabH homologous proteins with unknown functions. In this study, we found that only PXO_02706 (fabH1) encodes a functional FabH, the key enzyme in the production of branched-chain fatty acid, which is essential for the branched-chain diffusible signal factor family signals in Xoo. Interestingly, we found that FabH1 is not essential for fatty acid biosynthesis in Xoo. Pathogenicity analysis showed that loss of fabH1 caused a significant decrease in virulence of Xoo. Genetic and phenotypic analyses revealed that fabH1 plays a key role in multiple Xoo virulence-related activities, including exopolysaccharide (EPS) production, biofilm formation, motility, and resistance to environmental stresses.

Revised Enskog theory for Mie fluids: Prediction of diffusion coefficients, thermal diffusion coefficients, viscosities, and thermal conductivities.

Since the 1920s, the Enskog solutions to the Boltzmann equation have provided a route to predicting the transport properties of dilute gas mixtures. At higher densities, predictions have been limited to gases of hard spheres. In this work, we present a revised Enskog theory for multicomponent mixtures of Mie fluids, where the Barker-Henderson perturbation theory is used to calculate the radial distribution function at contact. With parameters of the Mie-potentials regressed to equilibrium properties, the theory is fully predictive for transport properties. The presented framework offers a link between the Mie potential and transport properties at elevated densities, giving accurate predictions for real fluids. For mixtures of noble gases, diffusion coefficients from experiments are reproduced within ±4%. For hydrogen, the predicted self-diffusion coefficient is within 10% of experimental data up to 200 MPa and at temperatures above 171K. Binary diffusion coefficients of the CO2/CH4 mixture from simulations are reproduced within 20% at pressures up to 14.7 MPa. Except for xenon in the vicinity of the critical point, the thermal conductivity of noble gases and their mixtures is reproduced within 10% of the experimental data. For other molecules than noble gases, the temperature dependence of the thermal conductivity is under-predicted, while the density dependence appears to be correctly predicted. Predictions of the viscosity are within ±10% of the experimental data for methane, nitrogen, and argon up to 300bar, for temperatures ranging from 233 to 523K. At pressures up to 500bar and temperatures from 200 to 800K, the predictions are within ±15% of the most accurate correlation for the viscosity of air. Comparing the theory to an extensive set of measurements of thermal diffusion ratios, we find that 49% of the model predictions are within ±20% of the reported measurements. The predicted thermal diffusion factor differs by less than 15% from the simulation results of Lennard-Jones mixtures, even at densities well exceeding the critical density.

A Stenotrophomonas maltophilia TetR-Like Transcriptional Regulator Involved in Fatty Acid Metabolism Is Controlled by Quorum Sensing Signals.

Stenotrophomonas maltophilia is an environmental bacterium as well as an emerging opportunistic multidrug-resistant pathogen. They use the endogenous diffusible signal factor (DSF) quorum sensing (QS) system to coordinate population behavior and regulate virulence processes but can also respond to exogenous N-acyl-homoserine lactone (AHL) signals produced by neighboring bacteria. The effect of these QS signals on the global gene expression of this species remains, however, unknown. Whole-transcriptome sequencing analyses were performed for exponential cultures of S. maltophilia K279a treated with exogenous DSF or AHLs. Addition of DSF and AHLs signals resulted in changes in expression of at least 2-fold for 28 and 82 genes, respectively. Interestingly, 22 of these genes were found upregulated by both QS signals, 14 of which were shown to also be induced during the stationary phase. Gene functions regulated by all conditions included lipid and amino acid metabolism, stress response and signal transduction, nitrogen and iron metabolism, and adaptation to microoxic conditions. Among the common top upregulated QS core genes, a putative TetR-like regulator (locus tag SMLT2053) was selected for functional characterization. This regulator controls its own β-oxidation operon (Smlt2053-Smlt2051), and it is found to sense long-chain fatty acids (FAs), including the QS signal DSF. Gene knockout experiments reveal that operon Smlt2053-Smlt2051 is involved in biofilm formation. Overall, our findings provide clues on the effect that QS signals have in S. maltophilia QS-related phenotypes and the transition from the exponential to the stationary phase and bacterial fitness under high-density growth. IMPORTANCE The quorum sensing system in Stenotrophomonas maltophilia, in addition to coordinating the bacterial population, controls virulence-associated phenotypes, such as biofilm formation, motility, protease production, and antibiotic resistance mechanisms. Biofilm formation is frequently associated with the persistence and chronic nature of nosocomial infections. In addition, biofilms exhibit high resistance to antibiotics, making treatment of these infections extremely difficult. The importance of studying the metabolic and regulatory systems controlled by quorum sensing autoinducers will make it possible to discover new targets to control pathogenicity mechanisms in S. maltophilia.

Kinetic and thermodynamic investigation on diffusion-limited crosslinking reaction behaviors of peroxide-induced low-density polyethylene

Crosslinking reaction behaviors can determine the network morphology and further influence macroscopic properties of polymers, while the current comprehension about crosslinking reaction behaviors of peroxide-induced low-density polyethylene (PLDPE) is quite lacking, which seriously limits its development and application. Here, for the first time, the crosslinking reaction behaviors of PLDPE are fully characterized and analyzed by combining kinetic and thermodynamic analysis. The kinetic behaviors are investigated by non-isothermal DSC and isothermal rheology methods, and thermodynamic characteristics of crosslinking reaction are analyzed by Arrhenius law and transition state theory. The results demonstrate that the crosslinking reaction of PLDPE involves complex order and autocatalysis reactions. Notably, the autocatalysis reaction is considered as the driving force of the whole crosslinking reaction. Furthermore, the autocatalysis reaction is proved to be strongly dependent on the diffusion of macromolecular chains under isothermal conditions, whereas the effect of diffusion on order reaction can be ignored. Given that, a new kinetic model incorporates the single diffusion factor to significantly describe the diffusion effect on the autocatalysis reaction during crosslinking, which grasps the complexity of crosslinking reaction mechanism. This model is able to characterize and predict the kinetic results of PLDPE crosslinking reaction very well. It provides an effective analysis methodology and an accurate kinetic model for characterizing and predicting the diffusion-limited crosslinking reaction behaviors of polymers.

DSF inactivator RpfB homologous FadD upregulated in Bradyrhizobium japonicum under iron limiting conditions

Phytopathogenic bacteria Xanthomonas campestris pv. campestris (Xcc) causes black rot and other plant diseases. Xcc senses diffusible signal factor (DSF) as a quorum-sensing (QS) signal that mediates mainly iron uptake and virulence. RpfB deactivates DSF in this DSF–QS circuit. We examined differential gene expression profiles of Bradyrhizobium japonicum under low versus high iron conditions and found that fadD and irr were upregulated under low iron (log2 fold change 0.825 and 1.716, respectively). In addition to having similar protein folding patterns and functional domain similarities, FadD shared 58% sequence similarity with RpfB of Xcc. The RpfB–DSF and FadD–DSF complexes had SWISSDock molecular docking scores of − 8.88 kcal/mol and − 9.85 kcal/mol, respectively, and the 100 ns molecular dynamics simulation results were in accord with the docking results. However, significant differences were found between the binding energies of FadD–DSF and RpfB–DSF, indicating possible FadD-dependent DSF turnover. The protein–protein interaction network showed that FadD connected indirectly with ABC transporter permease (ABCtp), which was also upregulated (log2 fold change 5.485). We speculate that the low iron condition may be a mimetic environmental stimulus for fadD upregulation in B. japonicum to deactivate DSF, inhibit iron uptake and virulence of DSF-producing neighbors. This finding provides a new option of using B. japonicum or a genetically improved B. japonicum as a potential biocontrol agent against Xcc, with the added benefit of plant growth-promoting properties.

Hydrochloric acid-modified fungi-microalgae biochar for adsorption of tetracycline hydrochloride: Performance and mechanism

Novel biochar (BC) was prepared by pyrolysis using Aspergillus oryzae-Microcystis aeruginosa (AOMA) flocs as raw materials. It has been used for tetracycline hydrochloride (TC) adsorption along with acid (HBC) and alkali modification (OHBC). Compared with BC (114.5 m2 g−1) and OHBC (283.9 m2 g−1), HBC had a larger specific surface area (SBET = 338.6 m2 g−1). Meanwhile, the Elovich kinetic and Sip isotherm models adequately fit the adsorption data, and intraparticle diffusion is the controlling factor for TC adsorption diffusion on HBC. Furthermore, the thermodynamic data indicated that this adsorption was endothermic and spontaneous. The experimental results demonstrated that there are multiple interactions during the adsorption reaction process, including pore filling, H-bonds, π-π interaction, hydrophobic affinity, and van der Waals forces. In general, biochar prepared from flocs of AOMA can be used to remediate tetracycline-contaminated water, and it is of great significance in improving resource utilization.

Multi-electron reaction and fast Al ion diffusion of δ-MnO2 cathode materials in rechargeable aluminum batteries via first-principle calculations

Rechargeable aluminum batteries with multi-electron reaction have a high theoretical capacity for next generation of energy storage devices. However, the diffusion mechanism and intrinsic property of Al insertion into MnO2 are not clear. Hence, based on the first-principles calculations, key influencing factors of slow Al-ions diffusion are narrow pathways, unstable Al-O bonds and Mn3+ type polaron have been identified by investigating four types of δ-MnO2 (O3, O’3, P2 and T1). Although Al insert into δ-MnO2 leads to a decrease in the spacing of the Mn-Mn layer, P2 type MnO2 keeps the long (spacious pathways) and stable (2.007–2.030 Å) Al-O bonds resulting in the lower energy barrier of Al diffusion of 0.56 eV. By eliminated the influence of Mn3+ (low concentration of Al insertion), the energy barrier of Al migration achieves 0.19 eV in P2 type, confirming the obviously effect of Mn3+ polaron. On the contrary, although the T1 type MnO2 has the sluggish of Al-ions diffusion, the larger interlayer spacing of Mn-Mn layer, causing by H2O could assist Al-ions diffusion. Furthermore, it is worth to notice that the multilayer δ-MnO2 achieves multi-electron reaction of 3|e|. Considering the requirement of high energy density, the average voltage of P2 (1.76 V) is not an obstacle for application as cathode in RABs. These discover suggest that layered MnO2 should keep more P2-type structure in the synthesis of materials and increase the interlayer spacing of Mn-Mn layer for providing technical support of RABs in large-scale energy storage.

The Role of Diffusible Signal Factors in Quorum Sensing for Improved Biocontrol Techniques

Quorum sensing (QS) is a mechanism by which bacteria communicate with each other to coordinate group behavior. One important aspect of QS is the production and detection of diffusible signal factors (DSFs), which are small molecules that can diffuse across bacterial membranes and trigger various responses. DSFs have been shown to play a crucial role in regulating a wide range of biological processes, including biofilm formation, virulence, and antibiotic resistance. In recent years, researchers have started to explore the potential of DSFs in biocontrol applications, where they can be used to interfere with the communication and coordination of pathogenic bacteria. This review discusses the role of DSFs in QS and how they can be utilized to develop improved biocontrol techniques. We also discuss the various strategies that have been developed to interfere with DSF-mediated QS, such as using DSF analogs or enzymes that degrade DSFs. We highlight some of the promising applications of DSFs in biocontrol, including their use as biocontrol agents as part of plant microbiomes. We argue that DSFs represent a promising avenue for developing novel and effective biocontrol strategies that can help address some of the most pressing challenges in agriculture and healthcare.

Recombinant production of a diffusible signal factor inhibits Salmonella invasion and animal carriage

ABSTRACT The complex chemical environment of the intestine is defined largely by the metabolic products of the resident microbiota. Enteric pathogens, elegantly evolved to thrive in the gut, use these chemical products as signals to recognize specific niches and to promote their survival and virulence. Our previous work has shown that a specific class of quorum-sensing molecules found within the gut, termed diffusible signal factors (DSF), signals the repression of Salmonella tissue invasion, thus defining a means by which this pathogen recognizes its location and modulates virulence to optimize its survival. Here, we determined whether the recombinant production of a DSF could reduce Salmonella virulence in vitro and in vivo. We found that the most potent repressor of Salmonella invasion, cis-2-hexadecenoic acid (c2-HDA), could be recombinantly produced in E. coli by the addition of a single exogenous gene encoding a fatty acid enoyl-CoA dehydratase/thioesterase and that co-culture of the recombinant strain with Salmonella potently inhibited tissue invasion by repressing Salmonella genes required for this essential virulence function. Using the well characterized E. coli Nissle 1917 strain and a chicken infection model, we found that the recombinant DSF-producing strain could be stably maintained in the large intestine. Further, challenge studies demonstrated that this recombinant organism could significantly reduce Salmonella colonization of the cecum, the site of carriage in this animal species. These findings thus describe a plausible means by which Salmonella virulence may be affected in animals by in situ chemical manipulation of functions essential for colonization and virulence.

Variation in leaf mesophyll anatomy of fern species imposes significant effects on leaf gas exchange, light capture, and leaf hydraulic conductance

The mesophyll anatomical traits are essential factors for efficient light capture, CO2 diffusion, and hydraulics in leaves. At the same time, leaf hydraulics are governed by the xylem anatomical traits. Thus, simultaneous analyses of the mesophyll and xylem anatomy will clarify the links among light capture, CO2 capture, and water use. However, such simultaneous analyses have been scarcely performed, particularly on non-seed plants. Using seven fern species, we first showed that fern species with a large mesophyll thickness had a high photosynthetic rate related to high light capture, high drought tolerance, and low leaf hydraulic conductance. The chloroplast surface area (Sc) per mesophyll thickness significantly decreased with an increase in mesophyll thickness, which may increase light diffusion and absorption efficiency in each chloroplast. The photosynthetic rate per Sc was almost constant with mesophyll thickness, which suggests that ferns enhance their light capture ability via the regulation of chloroplast density.

The Impact of Flooding on Snail Spread: The Case of Endemic Schistosomiasis Areas in Jiangxi Province, China.

Flooding is the main natural factor in snail diffusion, and it has a negative impact on schistosomiasis transmission. There are few studies on the spread and migration of snails following a flood; therefore, we aimed to investigate the influence of flooding on snail diffusion and explore the characteristics and laws of snail diffusion in Jiangxi Province. By using a retrospective survey and cross-sectional survey, the data on snail spreading in Jiangxi Province from 2017 to 2021 were collected. The distribution, nature, and area of snail spread were systematically analyzed in combination with the hydrological situation, types of region, and types of flood. From 2017 to 2021, a total of 120 snail-spread environments were found, including in 92 hilly areas and in 28 lake areas. The areas caused by flood and by other means numbered 6 and 114, respectively. The proportions of recurrence, expansion, and first-time occurrences were 43.42%, 38.16%, and 18.42%, respectively, and the 14 new snail environments were only distributed in the hilly areas. With the exception of 2018, the ratio of snail-spread areas in the hilly region was higher than that in lake region in other years. The average density of live snails was 0.0184-1.6617 no./0.1 m2 and 0.0028-0.2182 no./0.1 m2 in the hilly region. Among the 114 environments affected by floods, 86 consisted of hilly environments, including 66 spreading environments affected by rainstorm floods, and 20 rainstorm debris flow environments. There were 28 lake areas, of which 10 were in the Jiangxi section of Yangtze River and were affected by rainstorm floods. Snail spread following flooding has a certain 'lag effect,' and = simple annual changes in hydrological characteristics have little effect on the diffusion of snails or on their density = in the affected environment, but it is more closely related to local floods. The hilly environments are more susceptible to floods than the lake region, and the risk of snail spread is much higher in the hilly than in the lake region.

Global Stabilization of Delayed Feedback Financial System Involved in Advertisement under Impulsive Disturbance

Diffusion is an inevitable important factor in advertising dynamic systems. However, previous literature did not involve this important diffusion factor, and only involved the local stability of the advertising model. This paper develops a global stability criterion for the impulsive advertising dynamic model with a feedback term under the influence of diffusion. Since global stability requires the unique existence of equilibrium points, variational methods are employed to solve it in the infinite dimensional function space, and then a global stability criterion of the system is derived by way of the impulse inequality lemma and orthogonal decomposition of a class of Sobolev spaces. Numerical simulations verify the effectiveness of the proposed method.

Electrodeposition and corrosion performance of Ni-Co alloys with different cobalt contents

The deposition mechanism of Ni-Co alloys with different cobalt compositions plays an important role in the preparation and application of Ni-Co alloys by electrodeposition. Cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy were used to study the effect of the Co content on the electrodeposition mechanism of the plating. The surface morphology and crystal structure of the plated layers were studied by scanning electron microscopy and X-ray diffraction. The corrosion performance of nickel-cobalt alloys with different Co contents was analyzed by anodic polarization curves and electrochemical impedance spectroscopy. The results showed that during the early stage of electrocrystallization, increasing the CoSO4 content in the plating solution decreased the charge transfer resistance during nucleation and decreased the activation energy of nucleation/growth. Nucleation occurred via a three-dimensional transient nucleation mechanism, which was controlled by both diffusion and electrochemical factors. Compared with pure nickel, the Ni-Co alloy had a more pronounced (1 1 1) orientation and superior corrosion resistance. Plating with 10 wt% Co provided the best corrosion resistance.

Quorum sensing improves the plant growth-promoting ability of Stenotrophomonas rhizophila under saline-alkaline stress by enhancing its environmental adaptability.

Quorum sensing (QS) system has an essential function in plant growth-promoting rhizobacteria (PGPR) response to environmental stress and PGPR induction of plant tolerance to saline-alkaline stress. Nevertheless, there is a lack of understanding about how QS influences the growth-promoting effects of PGPR on plants. Stenotrophomonas rhizophila DSM14405T is a PGPR with a QS system, which can secrete diffusible signal factor (DSF), one of the QS signal molecules. In this study, we used the S. rhizophila wild type (WT) and an incompetent DSF production rpfF-knockout mutant strain to explore whether DSF-QS could affect the growth-promoting ability of PGPR in Brassica napus L. By measuring the seed germination rate, plant fresh weight, biomass, the total antioxidant capacity (T-AOC) level, and the content of chlorophyll in leaves, we found that DSF was unable to enhance the growth-promoting capacity of ΔrpfF and did not directly assist the plants in tolerating saline-alkaline stress. However, DSF aided S. rhizophila ΔrpfF in resisting stress during its effective period, and QS represents a continuous and precise regulatory mechanism. Altogether, our results show that DSF is helpful to improve the environmental adaptability and survival rate of S. rhizophila, thus indirectly improving the germination rate of seeds and helping plants grow under saline-alkaline stress. In this study, the mechanism of QS enhancing the environmental adaptability of PGPR was studied, which provided a theoretical basis for improving the application of PGPR to help plants better cope with saline-alkaline stress.

Study on flow separation and suction control of a compressor tandem cascade

To control the boundary layer separation on the front blade suction surface in a compressor tandem cascade at a high incidence angle, three suction schemes at different axial positions were introduced and the cascade performance improvement and separation flow control effects were investigated. Based on the experimental and numerical simulations, the aerodynamic performance of the prototype tandem cascade reaches the peak at the incidence angle of 5°. Continue to increase the incidence angle, the loss increases sharply, and the static pressure rise coefficient and diffusion factor begin to decrease. With the boundary layer suction on the suction surface of the front blade, fluid energy in the upstream boundary layer of the suction slot is increased, and the adverse pressure gradient downstream is decreased. By suction, the development and separation of the boundary layer are inhibited, and the loss in the tandem cascade is significantly reduced. The flow control effect of the suction scheme at the onset location of boundary layer separation is the best, and the flow loss can be reduced by about 34.9% with a suction flow rate of 1% at the incidence angle of 5°. The suction schemes have good flow control effects in a wide working range and broaden the available range of incidence angles of the tandem cascade. This study provides a reference for the design of tandem blades considering flow control and has a positive significance for improving compressor efficiency and pressure ratio.