Membrane Stress Research Articles

Activation of Ustilaginoidin Biosynthesis Gene uvpks1 in Villosiclava virens Albino Strain LN02 Influences Development, Stress Responses, and Inhibition of Rice Seed Germination.

Villosiclava virens (anamorph: Ustilaginoidea virens) is the pathogen of rice false smut (RFS), which is a destructive rice fungal disease. The albino strain LN02 is a natural white-phenotype mutant of V. virens due to its incapability to produce toxic ustilaginoidins. In this study, three strains including the normal strain P1, albino strain LN02, and complemented strain uvpks1C-1 of the LN02 strain were employed to investigate the activation of the ustilaginoidin biosynthesis gene uvpks1 in the albino strain LN02 to influence sporulation, conidia germination, pigment production, stress responses, and the inhibition of rice seed germination. The activation of the ustilaginoidin biosynthesis gene uvpks1 increased fungal tolerances to NaCl-induced osmotic stress, Congo-red-induced cell wall stress, SDS-induced cell membrane stress, and H2O2-induced oxidative stress. The activation of uvpks1 also increased sporulation, conidia germination, pigment production, and the inhibition of rice seed germination. In addition, the activation of uvpks1 was able to increase the mycelial growth of the V. virens albino strain LN02 at 23 °C and a pH from 5.5 to 7.5. The findings help in understanding the effects of the activation of uvpks1 in albino strain LN02 on development, pigment production, stress responses, and the inhibition of rice seed germination by controlling ustilaginoidin biosynthesis.

Comparison of Antibacterial Activities of Korean Pine (Pinus densiflora) Needle Steam Distillation Extract on Escherichia coli and Staphylococcus aureus Focusing on Membrane Fluidity and Genes Involved in Membrane Lipids and Stress.

The antibacterial activity and mechanism of Pinus densiflora extracts against Escherichia coli and Staphylococcus aureus were investigated. The growth inhibition tests of paper diffusion and optical density exhibited that the extracts have potent antibacterial potentials against foodborne pathogens. The measurement of membrane fluidity by fluorescence polarization has indicated that one of the antibacterial mechanisms involves the disruption of membrane integrity resulting in an increase in the membrane fluidity in both of E. coli and S. aureus. The alteration of fatty acid composition was accompanied by the disturbance of membranes thus shifting the proportion of saturated verses unsaturated fatty acids or trans fatty acids from 1.27:1 to 1.35:1 in E. coli and 1.47:1 to 2.31:1 in S. aureus, most likely to compensate for the increased membrane fluidity by means of a higher proportion of saturated fatty acids which is known to render rigidity in membranes. Realtime q-PCR (polymerase chain reaction) analysis of fatty acid synthetic genes and bacterial stress genes revealed that there was minimal influence of P. densiflora extracts on fatty acid genes except for fab I and the stress rpos in E. coli, and relatively greater impact on fatty acid genes and the stress sigB in S. aureus.

Manufacturing feasibility of a bend free ellipsoidal composite pressure vessel using automated fibre placement

Composite pressure vessels are attracting high research interest for their low weight and remarkable structural performance. Suppressing bending in pressure vessels offers increased pressure capacity by enabling the efficient membrane stress state. Variable angle tow (VAT) laminates have been shown theoretically to achieve this stress state in composite ellipsoids. This paper presents steps towards manufacturing such vessels using automated fibre placement (AFP). It was found that the bend free design is suited to tanks with diameters greater than ≈1400 mm when considering the VAT limitations of typical AFP equipment. When compared to a perfect ellipsoid, the addition of a polar boss reduced the portion of the tank satisfying the bend free criteria by 29.6 %, but also reduced deformation by 28.9 %. The layup considering overlaps was optimised, and manufacturing simulation and coupon manufacturing trials were used to verify thickness and steering radius predictions and visualise defect formation.

Bending theory of composite pressure vessels: A closed-form analytical approach

Composite pressure vessels are strategic for the present and future of the aerospace, transportation, and energy industries. These shell structures are utilized to store and transport liquids and gases and are principally composed of a cylindrical shell and two elliptical heads. The current rules for the structural design of composite pressure vessels make use of the membrane theory that excludes the bending of the structure. Nevertheless, the cylindrical shell and the elliptical heads present different curvature radii. These changes generate a localized bending deformation that determines an increase in the stress state as an effect of a local bending moment and shear force distributions that arise in the geometric transition zone. The stresses related to the bending effects die out rapidly, moving away from the junction plane, but they are sensibly higher than the membrane stress and, therefore, cannot be neglected in the mechanical assessment. Here, a closed-form analytical solution for the bending theory of composite shells is proposed. It can assist in the design of composite pressure vessels and drive the design towards reliable configurations for structural integrity. Using the Donnell–Mustari–Vlasov theory for thin-walled composite shells, the governing fourth-order differential equation is deduced and solved to obtain the displacements and stresses acting in the junction. The analytical results are successfully compared with those of reference finite element models for validation; their accuracy is proved considering different thicknesses, lay-ups, and flattening factors of the vessel

Immunity-linked genes are stimulated by a membrane stress pathway linked to Golgi function and the ARF-1 GTPase.

Infection response and other immunity-linked genes (ILGs) were first named in Caenorhabditis elegans-based expression after pathogen challenge, but many are also up-regulated when lipid metabolism is perturbed. Why pathogen attack and metabolic changes both increase ILGs is unclear. We find that ILGs are activated when phosphatidylcholine (PC) levels change in membranes of secretory organelles in C. elegans. RNAi targeting of the ADP-ribosylation factor arf-1, which disrupts the Golgi and secretory function, also activates ILGs. Low PC limits ARF-1 function, suggesting a mechanism for ILG activation via lipid metabolism, as part of a membrane stress response acting outside the ER. RNAi of selected ILGs uncovered defects in the secretion of two GFP reporters and the accumulation of a pathogen-responsive complement C1r/C1s, Uegf, Bmp1 (CUB) domain fusion protein. Our data argue that up-regulation of some ILGs is a coordinated response to changes in trafficking and may act to counteract stress on secretory function.

Modelling lipid rafts formation through chemo-mechanical interplay triggered by receptor-ligand binding.

Cell membranes, mediator of many biological mechanisms from adhesion and metabolism up to mutation and infection, are highly dynamic and heterogeneous environments exhibiting a strong coupling between biochemical events and structural re-organisation. This involves conformational changes induced, at lower scales, by lipid order transitions and by the micro-mechanical interplay of lipids with transmembrane proteins and molecular diffusion. Particular attention is focused on lipid rafts, ordered lipid microdomains rich of signalling proteins, that co-localise to enhance substance trafficking and activate different intracellular biochemical pathways. In this framework, the theoretical modelling of the dynamic clustering of lipid rafts implies a full multiphysics coupling between the kinetics of phase changes and the mechanical work performed by transmembrane proteins on lipids, involving the bilayer elasticity. This mechanism produces complex interspecific dynamics in which membrane stresses and chemical potentials do compete by determining different morphological arrangements, alteration in diffusive walkways and coalescence phenomena, with a consequent influence on both signalling potential and intracellular processes. Therefore, after identifying the leading chemo-mechanical interactions, the present work investigates from a modelling perspective the spatio-temporal evolution of raft domains to theoretically explain co-localisation and synergy between proteins' activation and raft formation, by coupling diffusive and mechanical phenomena to observe different morphological patterns and clustering of ordered lipids. This could help to gain new insights into the remodelling of cell membranes and could potentially suggest mechanically based strategies to control their selectivity, by orienting intracellular functions and mechanotransduction.

Effect of thermal manipulation on the biological and mechanical characteristics of horizontal platelet rich fibrin membranes

BackgroudRegardless of application scenarios, proper mechanical characteristics and degradation properties are prerequisites for horizontal platelet rich fibrin (H-PRF) to manifest its ability. Among the methods used to modify PRF, thermal manipulation is promising as it is easy to handle without adding extra additives. Yet there is no consensus on optimal temperature treatment. This study aimed to investigate the effects of heating on the biological and mechanical characteristics of H-PRF and explore the optimum heating temperature for H-PRF thermal treatment.MethodsWe employed a series of temperature gradients, room temperature, 50℃, 75℃, 90℃, 105℃. The microstructure and the mechanical properties were recorded by Scanning Electron Microscope (SEM) and tensile strength tests respectively. The degradation rate of H-PRF membranes was examined by digestion assay with plasmin and trypsin. The viability of cells within H-PRF membranes and the proliferation of osteoblasts cultured with extracts from different H-PRF groups was evaluated using CCK-8 assays.ResultsCompared with the nonheated group, overheated manipulation beyond 90℃ can significantly prolong the degradation properties for up to 3 to 4 weeks and enhance the mass stress of H-PRF membranes. A high-temperature treatment of 105℃ accompanied by the cell activity beneath H-PRF reduced more than half, and thus, the biological effect on human osteoblasts (hFOBs) also reduced dramatically.ConclusionsHigh thermal manipulation can prolong the degradation properties and enhance the mechanical properties of PRF membranes accompanied by the loss of biological effect.

Earthworm Coelomocyte Internalization of MoS2 Nanosheets: Multiplexed Imaging, Molecular Profiling, and Computational Modeling.

Fully understanding the cellular uptake and intracellular localization of MoS2 nanosheets (NSMoS2) is a prerequisite for their safe applications. Here, we characterized the uptake profile of NSMoS2 by functional coelomocytes of the earthworm Eisenia fetida. Considering that vacancy engineering is widely applied to enhance the NSMoS2 performance, we assessed the potential role of such atomic vacancies in regulating cellular uptake processes. Coelomocyte internalization and lysosomal accumulation of NSMoS2 were tracked by fluorescent labeling imaging. Cellular uptake inhibitors, proteomics, and transcriptomics helped to mechanistically distinguish vacancy-mediated endocytosis pathways. Specifically, Mo ions activated transmembrane transporter and ion-binding pathways, entering the coelomocyte through assisted diffusion. Unlike molybdate, pristine NSMoS2 (P-NSMoS2) induced protein polymerization and upregulated gene expression related to actin filament binding, which phenotypically initiated actin-mediated endocytosis. Conversely, vacancy-rich NSMoS2 (V-NSMoS2) were internalized by coelomocytes through a vesicle-mediated and energy-dependent pathway. Mechanistically, atomic vacancies inhibited mitochondrial transport gene expression and likely induced membrane stress, significantly enhancing endocytosis (20.3%, p < 0.001). Molecular dynamics modeling revealed structural and conformational damage of cytoskeletal protein caused by P-NSMoS2, as well as the rapid response of transport protein to V-NSMoS2. These findings demonstrate that earthworm functional coelomocytes can accumulate NSMoS2 and directly mediate cytotoxicity and that atomic vacancies can alter the endocytic pathway and enhance cellular uptake by reprogramming protein response and gene expression patterns. This study provides an important mechanistic understanding of the ecological risks of NSMoS2.

Identifying LiaFSR Residues Contributing to ExPortal Integrity and Response to Antimicrobials in Group A Streptococcus

Abstract Background Group A Streptococcus (GAS), or Streptococcus pyogenes, is responsible for a myriad of diseases (pharyngitis, scarlet fever, impetigo, toxic shock syndrome) of which several are prevalent in the pediatric population. The LiaFSR two-component regulatory system (TCS) and the ExPortal functional membrane microdomain (FMM) of GAS have been shown to coordinate the response to cell membrane stress when the bacterium is exposed to antimicrobials or antimicrobial peptides (AMPs). The ExPortal coordinates translocation and processing of secreted GAS proteins and contributes to sensing membrane. In an unstressed state, LiaF acts as an inhibitor of LiaS activity, both residing within the ExPortal. In a stressed state, such as exposure to antimicrobial agents, LiaF and S dissociate, allowing LiaS to phosphorylate LiaR, resulting in subsequent activation and expression of downstream target genes. Genomic analysis indicates a strict conservation of specific protein domains and certain amino acid residues in LiaF, S, and R, which suggests their critical involvement in the LiaFSR mechanism of action. We hypothesize that conserved amino acid residues in LiaFSR, such as the LiaF C-terminal domain (CTD) and a 3xK residue motif, are essential to ExPortal formation and maintenance and may contribute to differences in antimicrobial susceptibility and virulence. Methods Two different mutant strains were analyzed and compared to (wild-type) WT: one lacking the LiaF CTD (LiaF_∆CTD) and one mutagenized in the 3xK motif (LiaF_K91-93A). Five different assays were used to examine phenotypes associated with LiaFSR activity: SpeB protease activity through bacterial growth on milk plates, ExPortal integrity via fluorescence microscopy, diamide-induced oxidative stress tolerance, antimicrobial/antimicrobial peptide (AM/AMP) susceptibility, and a direct bactericidal assay in human blood (Lancefield). For the AM/AMP susceptibility, we tested 6 different antimicrobial agents with varying mechanisms of action: bacitracin, polymyxin B, LL-37, nisin, daptomycin, and HNP-1. Results Milk plate analysis revealed a significant decrease in SpeB production in the LiaF-∆CTD vs. WT, but no difference in LiaF-K91-93A relative to WT. During fluorescence microscopy, no significant differences were detected between foci of fluorescence of either mutant strain relative to WT. When exposed to diamide-induced oxidative stress, both mutants exhibited increased tolerance relative to WT. AM/AMP susceptibility assays did not reveal any significant differences for any antimicrobial agent between either mutant strain vs. WT. Finally, the Lancefield assay revealed a significant decrease in survival in human blood between both mutant strains and WT. Mutant strains also had significantly decreased survival relative to a strain lacking LiaF (∆LiaF). Conclusions The results of the AM/AMP susceptibility assay suggest that, unlike the LiaFSR system in Enterococcus, LiaF function does not contribute to LiaFSR-dependent susceptibility. Significant differences in survival in blood indicate that the LiaF residues studied are physiologically relevant in GAS infection. However, their exact mechanism underlying this contribution is being investigated. Future research will examine downstream gene regulation to elucidate the LiaFSR-associated mechanism of decreased survival in human blood, with the aim of defining determinants of GAS bacteremia.

Effects of the antimicrobial glabridin on membrane integrity and stress response activation in Listeria monocytogenes

Glabridin is a prenylated isoflavan which can be extracted from liquorice roots and has shown antimicrobial activity against foodborne pathogens and spoilage microorganisms. However, its application may be hindered due to limited information about its mode of action. In this study, we aimed to investigate the mode of action of glabridin using a combined phenotypic and proteomic approach on Listeria monocytogenes. Fluorescence and transmission electron microscopy of cells exposed to glabridin showed membrane permeabilization upon treatment with lethal concentrations of glabridin. Comparative proteomics analysis of control cells and cells exposed to sub-lethal concentrations of glabridin showed upregulation of proteins related to the two-component systems LiaSR and VirRS, confirming cell envelope damage during glabridin treatment. Additional upregulation of SigmaB regulon members signified activation of the general stress response in L. monocytogenes during this treatment. In line with the observed upregulation of cell envelope and general stress response proteins, sub-lethal treatment of glabridin induced (cross)protection against lethal heat and low pH stress and against antimicrobials such as nisin and glabridin itself. Overall, this study sheds light on the mode of action of glabridin and activation of the main stress responses to this antimicrobial isoflavan and highlights possible implications of its use as a naturally derived antimicrobial compound.

A semi-analytical model to predict residual stress distribution in thick wall girth weld with narrow gap welding

Benefited by its high efficiency and low cost, the narrow gap welding has been widely used in thick wall pressure equipment. Considering the fact that defects in welded joints inevitable, the safety assessments for welding equipment with residual stress are crucial. However, for the thick-wall equipment using narrow-gap welding, the current safety assessment standards specifying the residual stress distribution are not detailed or missing. In this paper, the through-wall residual stress of thick wall girth welds with narrow gap welding is studied. The stress components (bending stress, membrane stress and self-equilibrating stress) at the evaluation point are obtained by stress decomposition. The effects of the heat input, the wall thickness, the radius thickness ratio and the number of welding passes on residual stress are considered, respectively. The results show that the heat input only affects the distribution of bending stress and membrane stress. The axial and hoop bending stresses decrease with the increase of the wall thickness, and the hoop membrane stress is about 0.75 times material yield strength. With the increase of radius thickness ratio, the bending stress decreases while the hoop membrane stress increases. The stress distribution is fluctuating when the number of welding layers is small, which be expressed by trigonometric function. The distribution model of welding residual stress through the wall thickness is proposed. The stress distribution obtained by the proposed prediction model is in good agreement with the finite element calculation results.

Effect of bending stress parallel to the crack plane on J and the limit load of plates with surface cracks

The effect of bending stress parallel to the crack plane on J-integral of plates containing semi-elliptical surface cracks is investigated in this paper. Elastic and elastic–plastic finite element (FE) analyses are used to obtain J values for the surface-cracked plates under membrane stress or through-thickness bending stress normal to the crack plane or under biaxial membrane stresses plus through-thickness bending normal to the crack plane with/without bending stress parallel to the crack plane. The FE results show that, as predicted by linear elastic fracture mechanics, the applied bending stress parallel to the crack plane does not affect the crack tip elastic J. However, it does affect the elastic–plastic J. A limit load (or reference stress) solution for a plate containing a rectangular surface crack under combined biaxial membrane stresses and biaxial bending stresses is developed, which shows good correlation to the elastic–plastic FE J via the reference stress J scheme, for both cases with/without the bending stress parallel to the crack plane. Based on the results of the investigation, a newly-developed local limit load model is updated to include the effects of bending stress parallel to the crack plane for use in structural integrity assessments.

Improved Decal Transfer Method to Reduce Membrane Damage from Foreign Particles in Membrane Electrode Assembly

Foreign particles unintentionally embedded in the membrane electrolyte assembly may be detrimental to polymer electrolyte fuel cell durability by dissolution of contaminants or puncture of the membrane. The presence of incidental particles may also affect the fuel cell production cost by imposing more stringent and costly quality control equipment and cleanroom facilities to the manufacturers. The present work aims to understand the impact of foreign particles deposited at the membrane—catalyst layer interface on the decal transfer process and the quality of the resulting catalyst coated membrane. Additionally, this work explores process related opportunities to mitigate material damage from said particles. Several samples are fabricated by specifically placing representative silica particles on the membrane surface subsequently laminated with catalyst layer using different decal transfer procedures. Non-destructive 3D X-ray computed tomography reveals that the model particles substantially penetrate the membrane during regular decal transfer conditions, leading to a vulnerable membrane state or even complete puncture. However, a tuned decal transfer method with modified pressure application rate and optimized supporting layers is shown to reduce membrane damage up to 69%. Additionally, finite element modeling shows that the tuned method can reduce membrane stress during fuel cell operation and thus benefit durability.

Bioinspired Large‐Area Atomically‐Thin Graphene Membranes

AbstractNanoporous graphene membranes are attractive for molecular separations, but it remains challenging to maintain sufficient mechanical strength during scalable fabrication and module development. Inspired by the composite structure of cell membranes and cell walls, a large‐area atomically thin nanoporous graphene membrane supported by a fiber‐reinforced structure with strong interlamellar adhesion is designed. Compared with other graphene‐based membranes of large scale, the fracture stress, fracture strength, and tensile stiffness of the composite membranes can be enhanced by a factor of 17, 67, and 94, respectively. This fiber‐reinforced structure also confers stability of the composite membrane to different curvature states and repeated bending processes after 10 000 times, which provides an opportunity for modularization. The breathable function of such membrane with an ultrahigh gas permeance (≈8.6–23 L m−2 d−1 Pa−1) and an ultralow water vapor transportation rate (WVTR) (≈23–129 g L m−2 d−1) is observed, superior to most commercial materials. This work provides a facile method to fabricate large‐area graphene membranes and paves the road to practical application in the membrane separation field for other 2D films.

Innovative Insights on the Thin Square Plate Large Deflection Problem.

Thin plates subjected to transverse load and undergoing large deflections have been widely studied and published in the literature. However, there is still a lack of information and understanding about the membrane stresses created under large deflections and their associated Airy stress function, as displayed in the well-known von Kármán equations set. The present study aims at providing explicit expressions for the membrane stresses, the deflections, and the Airy stress function for a general square plate area vertically uniformly loaded to reach large deflection state. This was obtained by using the results of a high-fidelity finite element analysis applied on a lateral loaded simply supported thin square plate, which are then casted to yield approximate Fourier series expressions for the membrane stresses, deflections, and the Airy stress function. The stress map figures provide a good understanding of the critical points on the plate, while the explicit mathematical expressions enabled the calculation of deflections and stresses for the entire plate area. Among other interesting findings, the presence of relatively high tensile and compressive membrane stresses existing near the plate edges was revealed, which might lead to potential failure hazards. The derivatives of the deflections and the Airy stress function enabled the validation of the large deflections von Kármán equations set for the investigated case, and it turned out that the generated expressions for the stresses and the lateral deflection based on a high-fidelity finite element model satisfy the second equation with a good accuracy, while the first one remains to further be investigated. Moreover, using the generated explicit equations, the load influence on the deflections and stresses was also analyzed to yield general novel expressions for the medium and very large deflections states. To generalize the investigated case, the stresses and the deflections were non-dimensionalized so they can be used for any material and plate dimensions.

Biosensor-guided detection of outer membrane-specific antimicrobial activity against Pseudomonas aeruginosa from fungal cultures and medicinal plant extracts.

Pseudomonas aeruginosa responds to sub-lethal antimicrobial exposure by inducing the expression of lipopolysaccharide (LPS) surface modifications that mask antibiotic binding sites and contribute to repair and resistance of the outer membrane (OM). We exploit these membrane damage-responsive operons in a biosensor approach used to discover new antimicrobials that specifically target the OM. Chromosomal transcriptional luxCDABE reporters from the pmr (polymyxin resistance; aminoarabinose LPS modification) and speD2E2 (spermidine synthesis) operons are induced by validated outer membrane-acting agents including cationic antimicrobial peptides, cation chelators, ascorbic acid, detergents, and cell wall synthesis inhibitors cycloserine and bacitracin. To identify novel sources of OM-disrupting antimicrobials, we used these OM damage-responsive biosensors to screen a panel of fungal culture supernatants for novel antimicrobial and biosensor activity. Biosensor activity was used to determine the optimal time point of antimicrobial production from fungal supernatants and to guide the purification of active fractions after size-exclusion chromatography. Water and ethanol extracts of Chinese medicinal plants also proved to be a source of biosensor activity. The pathogen box is a 400-member drug library of potential antimicrobials, but none of these compounds induced our OM damage biosensors. This novel, sensitive, cell-based screening assay has potential for future discovery of lead compounds that specifically target the outer membrane, which is a significant barrier to antibiotic entry into Gram-negative bacteria.IMPORTANCENew approaches are needed to discover novel antimicrobials, particularly antibiotics that target the Gram-negative outer membrane. By exploiting bacterial sensing and responses to outer membrane (OM) damage, we used a biosensor approach consisting of polymyxin resistance gene transcriptional reporters to screen natural products and a small drug library for biosensor activity that indicates damage to the OM. The diverse antimicrobial compounds that cause induction of the polymyxin resistance genes, which correlates with outer membrane damage, suggest that these LPS and surface modifications also function in short-term repair to sublethal exposure and are required against broad membrane stress conditions.

FEATURES OF THE STRESS-DEFORMED STATE OF VERTICAL CYLINDRICAL TANKS UNDER EXTERNAL PRESSURE

The paper investigates the features of the stress-deformed state of cylindrical shells under wind pressure, taking into account its actual distribution on cylindrical structures. The purpose of the work is to obtain a qualitative picture of the distribution of stresses and deformations in the cylindrical wall of the tank under wind load, to determine the effect of wind load on both the strength and stability of the tank. Practical significance. It is known that the stresses caused by the action of the wind load, due to their small value, are safe from the point of view of strength, at the same time, obtaining quantitative values of the stress-deformed state main components of the tank under wind load has a certain practical significance. The task is to solve the problem of deformation of the cylindrical shell under external uneven pressure of the wind type. Content of research. The solution of the deformation problem was performed in a linear formulation for cylindrical shells with geometric parameters corresponding to the geometric parameters of vertical tanks with a volume of 1,000…30,000 m3. The solution of the problem was carried out for several loads of the shell with wind pressure of different intensity q = (0,2…1,2) qcrw. Such formulation of the problem made it possible to investigate the features of the stress-deformed state of cylindrical shells under wind pressure both at small values of the external load and at pressure values close to the critical ones, which is important from the standpoint of shell stability. Conclusions. The static calculation of the shells under wind pressure showed that membrane stresses in the annular direction prevail. Membrane stresses in the meridional direction are the second largest. The distribution of these stresses along the perimeter of the shell corresponds to the wind pressure plot. The main feature of the bending stress graphs is their wave character along the perimeter of the shell. Plots of radial displacements w and deformed shells also have a wave character. The size of such wave deviations is insignificant, but their length is close to the length of the waves of the shell protrusion when it loses its stability. Thus, the process of deformation of cylindrical shells under wind pressure is generally stable. The wind load itself is safe from the strength point of view. However, the obtained nature of the deformation, namely the wave deviations of the surface of the shell, can significantly affect the stability of the shell, which requires additional research.

RavA-ViaA antibiotic response is linked to Cpx and Zra2 envelope stress systems in Vibrio cholerae.

The RavA-ViaA complex was previously found to sensitize Escherichia coli to aminoglycosides (AGs) in anaerobic conditions, but the mechanism is unknown. AGs are antibiotics known for their high efficiency against Gram-negative bacteria. In order to elucidate how the expression of the ravA-viaA genes increases bacterial susceptibility to aminoglycosides, we aimed at identifying partner functions necessary for increased tolerance in the absence of RavA-ViaA, in Vibrio cholerae. We show that membrane stress response systems Cpx and Zra2 are required in the absence of RavA-ViaA, for the tolerance to AGs and for outer membrane integrity. In the absence of these systems, the ∆ravvia strain's membrane becomes permeable to external agents such as the antibiotic vancomycin.

A Finite Element Analysis Model-Based Study on the Effect of the Frame on Membrane Stresses in Proton Exchange Membrane Fuel Cells

The frame of a membrane electrode assembly (MEA) has an important impact on durability and reliability of a proton exchange membrane fuel cell (PEMFC). In this study, the finite element analysis method has been used to build a two-dimensional model that can quickly screen and compare different frame structures and improve the design. Simulation results show that the membrane in the gap between the frame and the active area will generate a large amount of stress, close to the yield strength of the membrane under this condition, after application of the pressure difference. Further, an appropriate frame structure can improve the structural consistency between the frame and the area with moving materials, reduce membrane stress and improve reliability. The problem of stress concentration on the membrane at the joint area is solved by introducing a double-layer frame structure to limit membrane deformation. Hence, this can effectively alleviate the impact of the gap at the joint area and improve the durability of MEA.

Atg8ylation as a host-protective mechanism against Mycobacterium tuberculosis.

Nearly two decades have passed since the first report on autophagy acting as a cell-autonomous defense against Mycobacterium tuberculosis. This helped usher a new area of research within the field of host-pathogen interactions and led to the recognition of autophagy as an immunological mechanism. Interest grew in the fundamental mechanisms of antimicrobial autophagy and in the prophylactic and therapeutic potential for tuberculosis. However, puzzling in vivo data have begun to emerge in murine models of M. tuberculosis infection. The control of infection in mice affirmed the effects of certain autophagy genes, specifically ATG5, but not of other ATGs. Recent studies with a more complete inactivation of ATG genes now show that multiple ATG genes are indeed necessary for protection against M. tuberculosis. These particular ATG genes are involved in the process of membrane atg8ylation. Atg8ylation in mammalian cells is a broad response to membrane stress, damage and remodeling of which canonical autophagy is one of the multiple downstream outputs. The current developments clarify the controversies and open new avenues for both fundamental and translational studies.