Search

This paper presents the water diffusion behaviour, tensile properties and fracture toughness of epoxy after it is aged in distilled and salt water in both steady and fluctuating conditions at a temperature of 50 °C. In steady and fluctuating conditions, the equilibrium water uptake of epoxy aged in salt water is lower than that in distilled water, but the diffusion rate is unaffected. The effects of the media and ageing condition on the tensile properties and fracture toughness are insignificant. The absorbed water (0.6–1.8%) improves the epoxy fracture toughness up to three times, which is indicated by the complex fracture surfaces of aged epoxy. [ABSTRACT FROM AUTHOR]

Despite enormous efforts, achieving efficacious levels of proteins inside mammalian cells remains one of the greatest challenges in biologics-based drug discovery and development. The inability of proteins to readily cross biological membranes precludes access to the wealth of intracellular targets and applications that lie within mammalian cells. Existing methods of delivery commonly suffer from an inability to target specific cells and tissues, poor endosomal escape, and limited in vivo efficacy. The aim of the present commentary is to highlight the potential of certain classes of bacterial toxins, which naturally deliver a large protein into the cytosolic compartment of target cells after binding a host cell-surface receptor with high affinity, as robust protein delivery platforms. We review the progress made in recent years toward demonstrating the utility of these systems at delivering a wide variety of protein cargo, with special attention paid to three distinct toxin-based platforms. We contend that with recent advances in protein deimmunization strategies, bacterial toxins are poised to introduce biologics into the inner sanctum of cells and treat a wealth of heretofore untreatable diseases with a new generation of therapeutics. [ABSTRACT FROM AUTHOR]

Abstract: Experimental and numerical studies have been undertaken on hybrid fibre–metal (aluminium–Glare) laminate (FML) doubler joints to investigate their static response under tension loading. The specimens either have the fibres parallel to the loading direction (spanwise) or perpendicular to the loading direction (chordwise). Inevitably sheets in these laminates butt together and these butts can affect the joint strength. The effect of the butt position was investigated. The spanwise specimen was found to have the highest strength followed by chordwise specimens without butts and finally chordwise specimens with butts. The most critical position for a butt was found to be adjacent to the doubler end. The ultimate strength for spanwise and chordwise specimens without butts was controlled by the failure in the Glare layer, however, for specimens with butts, the butts control the ultimate strength. A progressive damage numerical analysis was undertaken using cohesive zone elements to model failure in the Glare and in the adhesive layers. This modelling was found to be in good agreement with the experiment data both in terms of the strength and the failure mechanisms. [Copyright &y& Elsevier]

Since a robotic hand equipped with three-axis tactile sensors can detect not only grasped force caused by pinching motion but also slippage generated by sliding fingers, it can be applied to various tasks such as cap twisting, exploring object shape and detecting hardness. Although thin sheet handling is considered one of the more difficult tasks in robotics because of object flexibility and thinness, the versatility of the hand seems to accomplish this task. In this paper, we evaluate the sensing ability of this sheet thickness to obtain basic data for handling and turning thin flexible sheets. In this experiment, we used 1,000-yen bills as specimens because they have precise and stable size and mechanical properties. Experimental results showed that the robotic hand could not distinguish sheet numbers through a pinching grip causing normal force but could distinguish them through sliding fingers causing tangential force. [ABSTRACT FROM AUTHOR]

• The combined effect of hydrophobic nano calcium carbonate content and temperature on water absorption of epoxy nanocomposites was investigated. • Anomalous water absorption in the hydrophobic nano calcium carbonate/epoxy nanocomposites was observed. • Hydrophobic nano calcium carbonate increased water absorption of epoxy nanocomposites. • The tensile properties of hydrophobic nano calcium carbonate/epoxy nanocomposites were improved both in unaged and aged condition. In this study, we investigated the effects of the filler content and ageing temperature on the water absorption and tensile properties of hydrophobic nano-calcium carbonate (NCC)/epoxy nanocomposites. The NCC content of the nanocomposites was varied from 0 to 5 wt%, while the ageing temperature was set at 28, 45, and 55°C in a distilled water bath. The nanocomposites exhibited the non-Fickian behaviour at all the NCC contents and ageing temperatures. In general, the water absorption of the nanocomposites increased after the addition of NCC. Meanwhile, the diffusivity of the nanocomposites decreased with an increase in the NCC content; however, this decrease became less significant at higher ageing temperatures. Although the addition of 1–3 wt% NCC significantly increased the water uptake capability of the nanocomposites, it resulted in an improvement in their tensile properties at high temperatures and prolonged ageing times. [ABSTRACT FROM AUTHOR]

Type IV pili (T4P) contain hundreds of major subunits, but minor subunits are also required for assembly and function. Here we show that Pseudomonas aeruginosa minor pilins prime pilus assembly and traffic the pilus-associated adhesin and anti-retraction protein, PilY1, to the cell surface. PilV, PilW, and PilX require PilY1 for inclusion in surface pili and vice versa, suggestive of complex formation. PilE requires PilVWXY1 for inclusion, suggesting that it binds a novel interface created by two or more components. FimU is incorporated independently of the others and is proposed to couple the putative minor pilin-PilY1 complex to the major subunit. The production of small amounts of T4P by a mutant lacking the minor pilin operon was traced to expression of minor pseudopilins from the P. aeruginosa type II secretion (T2S) system, showing that under retraction-deficient conditions,T2Sminor subunits can prime T4P assembly. Deletion of all minor subunits abrogated pilus assembly. In a strain lacking the minor pseudopilins, PilVWXY1 and either FimU or PilE comprised the minimal set of components required for pilus assembly. Supporting functional conservation of T2S and T4P minor components, our 1.4 Å crystal structure of FimU revealed striking architectural similarity to its T2S ortholog GspH, despite minimal sequence identity. We propose that PilVWXY1 form a priming complex for assembly and that PilE and FimU together stably couple the complex to the major subunit. Trafficking of the anti-retraction factor PilY1 to the cell surface allows for production of pili of sufficient length to support adherence and motility. [ABSTRACT FROM AUTHOR]

Abstract: Experimental studies have been undertaken investigating the effect of moisture on the fatigue response of adhesively bonded monolithic single lap joints and laminated doublers loaded in bending, both made of the same materials. The joints were aged in deionised water at a temperature of 50°C for up to 2 years exposure. The backface strain technique was employed to monitor damage initiation and propagation in the joints. The test results show that the fatigue life degraded with increasing moisture content and tended to level off when approaching saturation. The failure surfaces were cohesive in the adhesive. Numerical fatigue modelling has been undertaken to predict the fatigue response of these joints utilising a strain-based fatigue damage law integrated with a bilinear traction-separation cohesive zone model. The residual stresses due to thermal and swelling strain were included in the model. Good agreement was found between the predicted fatigue response and the experimental results. [Copyright &y& Elsevier]

Abstract: A cohesive zone model has been used to model the progressive damage in adhesively bonded aluminium monolithic single lap joints and laminated doublers. The backface strain technique was used to monitor the damage process in the adhesive layer and was also key in the calibration of a unique set of cohesive zone properties in the single lap joint. Further, this backface strain technique has been successfully used to assess the effect of substrate plasticity, position of cohesive elements, traction and fracture energy, and adhesive fillet in a monolithic single joint. The calibrated cohesive properties have then been successfully used to predict the static strength and backface strain response of the doublers in bending. [Copyright &y& Elsevier]

Abstract: The aim of this research is to investigate the effect of moisture on the static response of adhesively bonded monolithic single lap joints and laminated doublers loaded in bending. All joints were made of aluminium alloy Al 2024-T3 bonded using epoxy film adhesive FM 73M OST. The joints were aged in deionised water at a temperature of 50°C for up to 2 years exposure. The use of different widths of specimen (5mm for monolithic single lap joints and 15mm for laminated doublers) allowed both full and partial saturation of the adhesive layer. The bulk adhesive has been characterised to obtain the coefficient of moisture diffusion, the coefficient of thermal and moisture expansion and the moisture dependent mechanical properties. The testing results showed that the mechanical properties degraded in a linear way with the moisture content. The residual strength after exposure decreased with increasing moisture content (exposure time) and tended to level off towards saturation. The damage evolution and failure of the joint has been successfully monitored using the backface strain technique and in-situ video microscopy. Progressive damage finite element modelling using a moisture dependent, bilinear traction-separation law has been undertaken to predict the residual strength. Residual stresses due to thermal and swelling strains in the adhesive layer have been included; however their effect on the predicted static strength was not significant. Good agreement was found between the predicted residual strength and the experimental result. [Copyright &y& Elsevier]

Abstract: Experimental and numerical studies have been undertaken on metal laminate (ML) doublers and hybrid fibre-metal (aluminium–Glare) laminate (FML) doublers to investigate their static and fatigue response under tension loading. Inevitably sheets in these laminates butt together and these butts can affect the joint strength. Progressive damage modelling, including the damage in the adhesive bondline, the butt, the metal and the fibre has been undertaken in both static and fatigue loading. This modelling was found to be in good agreement with the experiment data in terms both of the strength and the failure mechanisms. In ML, the butt influenced the static and fatigue response. In hybrid FML, the specimens either have the fibres parallel to the loading direction (spanwise) or perpendicular to the loading direction (chordwise). The spanwise specimen was found to have the highest strength followed by chordwise specimens without butts and finally chordwise specimens with butts. The most critical position for a butt was found to be adjacent to the doubler end. Without butts the static strength for spanwise and chordwise specimens was controlled by the failure in the Glare layer whilst the fatigue failure was precipitated by failure in the aluminium sheet. [Copyright &y& Elsevier]

This paper presents the experimental and numerical investigation of the residual strength of steel-composites joints aged in distilled and salt water under steady and fluctuating conditions at a temperature of 45 °C. The adhesive and the composites adherend had been characterized to obtain water absorption behavior and water-dependent mechanical properties. It was found that under the steady condition, the residual strength of the joints aged in distilled water was lower than that aged in salt water; however, under the fluctuating condition, the residual strength of the joints aged in salt water was lower than that aged in distilled water. Overall, the residual strength of the joints aged in salt water under the fluctuating condition was the lowest. Sequentially water diffusion and progressive damage finite element modeling of the joints considering the failure mode have been undertaken. The predicted residual strengths included the cohesive and interfacial failures were in reasonably agreement with the experimental results. [ABSTRACT FROM AUTHOR]

Clostridium difficile is a major nosocomial pathogen that produces two exotoxins, TcdA and TcdB, with TcdB thought to be the primary determinant in human disease. TcdA and TcdB are large, multidomain proteins, each harboring a cytotoxic glucosyltransferasedomainthat is delivered into the cytosol from endosomes via a translocation domain after receptor-mediated endocytosis of toxinsfromthe cell surface. Although there are currentlynoknown host cell receptors for TcdA, three cell-surface receptors for TcdB have been identified: CSPG4, NECTIN3, and FZD1/2/7. The sites on TcdB that mediate binding to each receptor are not defined. Furthermore, it is not known whether the combined repetitive oligopeptide (CROP) domain is involved in or required for receptor binding. Here, in a screen designed to identify sites inTcdBthat are essential for target cell intoxication, we identified a region at the junction of the translocation and the CROP domains that is implicated in CSPG4 binding. Using a series of C-terminal truncations, we show that the CSPG4-binding site on TcdB extends into the CROP domain, requiring three short repeats for binding and for full toxicityonCSPG4-expressing cells. Consistent with the location of the CSPG4-binding site on TcdB, we show that the anti-TcdB antibody bezlotoxumab, which binds partially within the first three short repeats, prevents CSPG4 binding to TcdB. In addition to establishing the binding region for CSPG4, this work ascribes for the first time a role in TcdB CROPs in receptor binding and further clarifies the relative roles of host receptors in TcdB pathogenesis. [ABSTRACT FROM AUTHOR]

Many bacterial pathogens, including Pseudomonas aeruginosa, use type IVa pili (T4aP) for attachment and twitching motility. T4aP are composed primarily of major pilin subunits, which are repeatedly assembled and disassembled to mediate function. A group of pilin-like proteins, the minor pilins FimU and PilVWXE, prime pilus assembly and are incorporated into the pilus. We showed previously that minor pilin PilE depends on the putative priming subcomplex PilVWX and the non-pilin protein PilY1 for incorporation into pili, and that with FimU, PilE may couple the priming subcomplex to the major pilin PilA, allowing for efficient pilus assembly. Here we provide further support for this model, showing interaction of PilE with other minor pilins and the major pilin. A 1.25 Å crystal structure of PilEΔ1-28 shows a typical type IV pilin fold, demonstrating how it may be incorporated into the pilus. Despite limited sequence identity, PilE is structurally similar to Neisseria meningitidis minor pilins PilXNm and PilVNm, recently suggested via characterization of mCherry fusions to modulate pilus assembly from within the periplasm. A P. aeruginosa PilE-mCherry fusion failed to complement twitching motility or piliation of a pilE mutant. However, in a retraction-deficient strain where surface piliation depends solely on PilE, the fusion construct restored some surface piliation. PilE-mCherry was present in sheared surface fractions, suggesting that it was incorporated into pili. Together, these data provide evidence that PilE, the sole P. aeruginosa equivalent of PilXNm and PilVNm, likely connects a priming subcomplex to the major pilin, promoting efficient assembly of T4aP. [ABSTRACT FROM AUTHOR]

A number of Gram-negative pathogens utilize type III secretion systems (T3SSs) to inject bacterial effector proteins into the host. An important component of T3SSs is a conserved ATPase that captures chaperone-effector complexes and energizes their dissociation to facilitate effector translocation. To date, there has been limited work characterizing the chaperone-T3SS ATPase interaction despite it being a fundamental aspect of T3SS function. In this study, we present the 2.1 Å resolution crystal structure of the Salmonella enterica SPI-2-encoded ATPase, SsaN. Our structure revealed a local and functionally important novel feature in helix 10 that we used to define the interaction domain relevant to chaperone binding. Wemodeled the interaction between the multicargo chaperone, SrcA, and SsaN and validated this model using mutagenesis to identify the residues on both the chaperone and ATPase that mediate the interaction. Finally, we quantified the benefit of this molecular interaction on bacterial fitness in vivo using chromosomal exchange of wild-type ssaN with mutants that retain ATPase activity but no longer capture the chaperone. Our findings provide insight into chaperone recognition by T3SS ATPases and demonstrate the importance of the chaperone-T3SS ATPase interaction for the pathogenesis of Salmonella. [ABSTRACT FROM AUTHOR]