A new mechanistic model has been established for the chemical and electrochemical mechanisms controlling nickel–aluminium bronze crevice corrosion. The crevice corrosion was initially confined to ...eutectoid regions with slight attack of the copper rich α-phase within the α+κ
III eutectoid. In the presence of high chloride concentrations, copper and aluminium complexes form and the hydrolysis of these complexes leads to the acidification of the crevice solution chemistry. As the crevice solution becomes increasingly acidic the initial protection of the κ-phases due to their higher aluminium contents is lost and become anodic to the α-phase. The continuous nature of the κ
III-phase makes it vulnerable with an ∼80
μm depth of attack after only the first month which is accompanied by internal copper redeposited at cathodic sites. Crevice corrosion of copper-based alloys is often reported to be controlled by a copper-ion concentration cell, however, for nickel–aluminium bronze it appears that primarily the crevice corrosion propagation results from a combined action of localised acidification and differential aeration between the bold and occluded zones. This mechanistic understanding provides further insights in to the development of crevice corrosion experienced by nickel–aluminium bronze after long-term exposures to natural seawater for up to 3 years.
A plasmonic bioassay for the specific detection of human influenza virus has been developed based on gold nanoparticles functionalised with a designed and synthesised thiolated trivalent ...α2,6-thio-linked sialic acid derivative. The glyconanoparticles consist of the thiolated trivalent α2,6-thio-linked sialic acid derivative and a thiolated polyethylene glycol (PEG) derivative self-assembled onto the gold surface. Varying ratios of the trivalent α2,6-thio-linked sialic acid ligand and the PEG ligand were used; a ratio of 25:75 was found to be optimum for the detection of human influenza virus X31 (H3N2). In the presence of the influenza virus a solution of the glyconanoparticles aggregate following the binding of the trivalent α2,6-thio-linked sialic acid ligand to the haemagglutinin on the surface of the virus. The aggregation of the glycoparticles with the influenza virus induces a colour change of the solution within 30 min. Non-purified influenza virus in allantoic fluid was successfully detected using the functionalised glyconanoparticles. A comparison between the trivalent and a monovalent α2,6-thio-linked sialic acid functionalised nanoparticles confirmed that more rapid results, with greater sensitivity, were achieved using the trivalent ligand for the detection of the X31 virus. Importantly, the glyconanoparticles were able to discriminate between human (α2,6 binding) and avian (α2,3 binding) RG14 (H5N1) influenza virus highlighting the binding specificity of the trivalent α2,6-thio-linked sialic acid ligand.
Nickel–aluminium bronze (NAB) alloys show good corrosion resistance under marine conditions. The corrosion behaviour of cast and wrought NAB alloys is illustrated in this work through a range of ...electrochemical techniques including open-circuit potentiometry with time, oxygen reduction voltammetry, NAB dissolution voltammetry, potential step (or flow step) current transients and linear polarisation resistance. The galvanic coupling of NAB to stainless steel or copper is examined by zero resistance ammetery. The importance of using controlled flow working electrodes is illustrated by the use of a rotating disc electrode, a rotating cylinder electrode and a bimetallic (NAB/copper–nickel) rotating cylinder electrode. In addition to controlling the hydrodynamics, such electrodes allow charge transfer data to separate from those of mass transport control under mixed kinetic control. Longer term seawater immersion trials on planar coupons coupled to titanium or cupronickel are also reported. The relative contributions of erosion and corrosion attack are considered using a wall-jet electrode and the corrosion characteristics of NAB are compared to those of copper and copper–nickel in chloride media.
Marine bacteria contribute significantly towards the fouling consortium, both directly (modern foul release coatings fail to prevent "slime" attachment) and indirectly (biofilms often excrete ...chemical cues that attract macrofouling settlement). This study assessed the natural product anti-biofilm performance of an extract of the seaweed, Chondrus crispus, and two isolated compounds from terrestrial sources, (+)-usnic acid and juglone, against two marine biofilm forming bacteria, Cobetia marina and Marinobacter hydrocarbonoclasticus. Bioassays were developed using quantitative imaging and fluorescent labelling to test the natural products over a range of concentrations against initial bacterial attachment. All natural products affected bacterial attachment; however, juglone demonstrated the best anti-biofilm performance against both bacterial species at a concentration range between 5-20 ppm. In addition, for the first time, a dose-dependent inhibition (hormetic) response was observed for natural products against marine biofilm forming bacteria.
Taking advantage of their optical transparency, we clearly observed the third stage infective juveniles (IJs) of Steinernema feltiae freezing under a cryo-stage microscope. The IJs froze when the ...water surrounding them froze at -2°C and below. However, they avoid inoculative freezing at -1°C, suggesting cryoprotective dehydration. Freezing was evident as a sudden darkening and cessation of IJs' movement. Freeze substitution and transmission electron microscopy confirmed that the IJs of S. feltiae freeze intracellularly. Ice crystals were found in every compartment of the body. IJs frozen at high sub-zero temperatures (-1 and -3°C) survived and had small ice crystals. Those frozen at -10°C had large ice crystals and did not survive. However, the pattern of ice formation was not well-controlled and individual nematodes frozen at -3°C had both small and large ice crystals. IJs frozen by plunging directly into liquid nitrogen had small ice crystals, but did not survive. This study thus presents the evidence that S. feltiae is only the second freeze tolerant animal, after the Antarctic nematode Panagrolaimus davidi, shown to withstand extensive intracellular freezing.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Isolated and established in culture from the Antarctic in 1988, the nematode Panagrolaimus davidi has proven to be an ideal model for the study of adaptation to the cold. Not only is it the ...best-documented example of an organism surviving intracellular freezing but it is also able to undergo cryoprotective dehydration. As part of an ongoing effort to develop a molecular understanding of this remarkable organism, we have assembled both a transcriptome and a set of genomic scaffolds. We provide an overview of the transcriptome and a survey of genes involved in temperature stress. We also explore, in silico, the possibility that P. davidi will be susceptible to an environmental RNAi response, important for further functional studies.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Background
Two new subclades of influenza A(H3N2) viruses became prominent during the 2014‐2015 Northern Hemisphere influenza season. The HA glycoproteins of these viruses showed sequence changes ...previously associated with alterations in receptor‐binding properties. To address how these changes influence virus propagation, viruses were isolated and propagated in conventional MDCK cells and MDCK‐SIAT1 cells, cells with enhanced expression of the human receptor for the virus, and analysed at each passage.
Methods
Gene sequence analysis was undertaken as virus was passaged in conventional MDCK cells and MDCK‐SIAT1 cells. Alterations in receptor recognition associated with passage of virus were examined by haemagglutination assays using red blood cells from guinea pigs, turkeys and humans. Microneutralisation assays were performed to determine how passage‐acquired amino acid substitutions and polymorphisms affected virus antigenicity.
Results
Viruses were able to infect MDCK‐SIAT1 cells more efficiently than conventional MDCK cells. Viruses of both the 3C.2a and 3C.3a subclades showed greater sequence change on passage in conventional MDCK cells than in MDCK‐SIAT1 cells, with amino acid substitutions being seen in both HA and NA glycoproteins. However, virus passage in MDCK‐SIAT1 cells at low inoculum dilutions showed reducing infectivity on continued passage.
Conclusions
Current H3N2 viruses should be cultured in the MDCK‐SIAT1 cell line to maintain faithful replication of the virus, and at an appropriate multiplicity of infection to retain infectivity.
Abstract We present an in-depth failure analysis of two large diameter bearing metal-on-polymer (MoP) modular total hip replacements, which have required revision surgery due to pseudotumour ...formation. The failure analysis showed a discrete pattern of material loss from the distal end of the head taper/stem trunnion interface. We postulate that the use of a proximal contacting taper design had provided insufficient mechanical locking between the head and the stem, enabling the head to toggle on the trunnion. In addition, the difference in angle between the taper and the trunnion formed a crevice between the two components. Through a combination of crevice environment, mechanically assisted corrosion, mechanical wear and erosion; debris and metal-ions have been released resulting in the adverse local tissue reactions (ALTR).
Distinct pools of the bone morphogenetic protein (BMP) Glass bottom boat (Gbb) control structure and function of the Drosophila neuromuscular junction. Specifically, motoneuron-derived Gbb regulates ...baseline neurotransmitter release, whereas muscle-derived Gbb regulates neuromuscular junction growth. Yet how cells differentiate between these ligand pools is not known. Here we present evidence that the neuronal Gbb-binding protein Crimpy (Cmpy) permits discrimination of pre- and postsynaptic ligand by serving sequential functions in Gbb signaling. Cmpy first delivers Gbb to dense core vesicles (DCVs) for activity-dependent release from presynaptic terminals. In the absence of Cmpy, Gbb is no longer associated with DCVs and is not released by activity. Electrophysiological analyses demonstrate that Cmpy promotes Gbb’s proneurotransmission function. Surprisingly, the Cmpy ectodomain is itself released upon DCV exocytosis, arguing that Cmpy serves a second function in BMP signaling. In addition to trafficking Gbb to DCVs, we propose that Gbb/Cmpy corelease from presynaptic terminals defines a neuronal protransmission signal.
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•Crimpy traffics Gbb to presynaptic dense core vesicles•Presynaptic release of Gbb is absolutely dependent on neuronal activity and Crimpy•Crimpy promotes Gbb’s proneurotransmission function•The Crimpy ectodomain is itself cleaved and subject to activity-dependent release
At the Drosophila neuromuscular junction, presynaptic Gbb promotes neurotransmitter release, whereas postsynaptic Gbb promotes NMJ growth. James et al. find that Crimpy enables separation of these two signals at the synapse. Crimpy marks the presynaptic ligand pool by trafficking Gbb into dense core vesicles for activity-dependent release.
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