► Literature review concerning mechanical anchorage of FRP tendons. ► AFRP, GFRP and CFRP used as tendon material. ► Bonded- and mechanical anchorage systems are illustrated. ► Survey of FE- and ...analytical models used for anchorage evaluation. ► Comparing steel- and FRP systems, no competitive FRP prestressing system have yet been developed.
High tensile strength, good resistance to degradation and creep, low weight and, to some extent, the ability to change the modulus of elasticity are some of the advantages of using prestressed, unidirectional FRP (Fibre Reinforced Polymer) tendon systems. Bonded and non-bonded versions of these systems have been investigated over the last three decades with results showing that prestressing systems can be very efficient when the FRP properties are properly exploited. However, there are often concerns as to how to exploit those properties to the full and how to achieve reliable anchorage with such systems. This is especially important in external post-tensioned tendon systems, where the anchorage points are exposed to the full load throughout the life span of the structure. Consequently, there are large requirements related to the long-term capacity and fatigue resistance of such systems. Several anchorage systems for use with Aramid, Glass and Carbon FRP tendons have been proposed over the last two decades. Each system is usually tailored to a particular type of tendon. This paper presents a brief overview of bonded anchorage applications while the primary literature review discusses three methods of mechanical anchorage: spike, wedge and clamping. Some proposals for future research are suggested. In general, the systems investigated showed inconsistent results with a small difference between achieving either a successful or an unsuccessful anchorage. These inconsistencies seem to be due to the brittleness of the tendons, low strength perpendicular to the fibre direction and insufficient stress transfer in the anchorage/tendon interface. As a result, anchorage failure modes tend to be excessive principal stresses, local crushing and interfacial slippage (abrasive wear), all of which are difficult to predict.
•FRGC-jacketing technique increased the loading performance of RC beams.•FRGC-jacketed beams exhibited high energy absorption capacity.•The flexural strength of FRGC-jacketed beams was modelled ...analytically.
Fibre-reinforced geopolymer composites (FRGC) are drawing interest as potential repairing and strengthening materials for concrete elements due to their desirable properties. They are known to have good mechanical bond with the concrete substrate and steel reinforcement, good fire resistance, greater durability in corrosive environments, and lower creep and shrinkage characteristics. However, the main challenge in their practical application is the lack of design standards and the structural performance of FRGC-rehabilitated concrete elements has not been fully investigated. In this paper, the result obtained from an experimental study on the flexural behavior of reinforced concrete (RC) beams jacketed by hybrid FRGC is reported. Six repair and strengthening configurations were adopted in this study including jacketing at the bottom, two and three sides of the beam with at least 25 mm thick FRGC layer. Twelve FRGC-jacketed and two control beams were subjected to four-point bending test to determine their loading performance, cracking response, ductility and energy absorption capacity. In addition, an analytical model was developed to predict the ultimate moment capacity of the jacketed beams. The results showed that FRGC-jacketing technique increased the cracking, yielding and ultimate load of the initial RC beams by up to 167%, 62% and 62% respectively. Among the seven repair and strengthening patterns, the bottom and three-sides jacketing provided less ductile response, nevertheless, it offered a 32% increase on the energy absorption value of the initial RC beam. It also indicated that all jacketed RC beams displayed no sign of overlay delamination up to failure, confirming a bond excellence between the FRGC and concrete substrate. The model predicting the flexural moment capacity of the FRGC jacketed beams compared reasonably with the experimental results with error value of 4–7%.
Red mark syndrome (RMS) is a skin disease of rainbow trout, the prevalence of which has increased in Europe over the last two decades. Hallmark symptoms are large, haemorrhagic skin lesions. It is ...believed that the disease is bacterial and caused by a Midichloria-like organism (MLO). However, the bacterium has never been isolated or cultured in vitro, and is only known from its 16S rDNA sequence. Thus there is no vaccine for the disease, and no other officially recognized way of ameliorating RMS symptoms.
Here we investigate for the first time the effect on RMS of in-feed treatment with three types of antibiotics: Florfenicol, oxolinic acid and oxytetracycline under controlled experimental conditions using a cohabitation model of disease transfer.
In short, 160 rainbow trout were cohabited with seeder fish, which showed the classical skin pathology of RMS and tested positive for MLO. After 55 days at 12 °C the cohabitants (now weighing 223 ± 57 g) started showing very early signs of RMS-related skin pathology and were randomly divided into 8 tanks (4 treatment groups in duplicate). The fish were fed medicated (or control) feed for 10 days. The fish were evaluated visually after 7 and 14 days and finally terminated after 20 days where skin samples were taken for testing for MLO by qPCR.
All three types of antibiotics significantly affected the monitored disease parameters: Macroscopic skin lesions were less severe and less MLO 16S rDNA could be detected from skin samples by qPCR in antibiotics-fed fish compared to fish that had not received antibiotics.
•Florfenicol, oxolinic acid and oxytetracycline all reduced RMS skin pathology.•Florfenicol, oxolinic acid and oxytetracycline all reduced MLO 16S rDNA copy numbers.•Results support existing evidence that RMS is caused by a bacterium.•Antibiotic treatment is efficient for RMS, but may have limited practical use.
The widespread environmental presence and commercial use of nanoparticles have raised significant health concerns as a result of many in vitro and in vivo assays indicating toxicity of a wide range ...of nanoparticle species. Many of these assays have identified the ability of nanoparticles to damage cell membranes. These interactions can be studied in detail using artificial lipid bilayers, which can provide insight into the nature of the particle-membrane interaction through variation of membrane and solution properties not possible with cell-based assays. However, the scope of these studies can be limited because of the low throughput characteristic of lipid bilayer platforms. We have recently described an easy to use, parallel lipid bilayer platform which we have used to electrically investigate the activity of 60 nm diameter amine and carboxyl modified polystyrene nanoparticles (NH2-NP and COOH-NP) with over 1000 lipid bilayers while varying lipid composition, bilayer charge, ionic strength, pH, voltage, serum, particle concentration, and particle charge. Our results confirm recent studies finding activity of NH2-NP but not COOH-NP. Detailed analysis shows that NH2-NP formed pores 0.3-2.3 nm in radius, dependent on bilayer and solution composition. These interactions appear to be electrostatic, as they are regulated by NH2-NP surface charge, solution ionic strength, and bilayer charge. The ability to rapidly measure a large number of nanoparticle and membrane parameters indicates strong potential of this bilayer array platform for additional nanoparticle bilayer studies.
Femtosecond, two-photon-absorption laser-induced fluorescence (fs-TALIF) is employed to measure space- and time-resolved distributions of atomic hydrogen and oxygen in moderate-pressure, ...non-equilibrium, nanosecond-duration pulsed-discharge plasmas. Temporally and spatially resolved hydrogen and oxygen TALIF images are obtained over a range of low-temperature plasmas in mixtures of helium and argon at 100 Torr total pressure. The high-peak-intensity, low-average-energy fs pulses combined with the increased spectral bandwidth compared to traditional ns-duration laser pulses provide a large number of photon pairs that are responsible for the two-photon excitation, which results in an enhanced TALIF signal. Krypton and xenon TALIF are used for quantitative calibration of the hydrogen and oxygen concentrations, respectively, with similar excitation schemes being employed. This enables 2D collection of atomic-hydrogen and -oxygen TALIF signals with absolute number densities ranging from 2 × 1012 cm−3 to 6 × 1015 cm−3 and 1 × 1013 cm−3 to 3 × 1016 cm−3, respectively. These 2D images are the first application of TALIF imaging in moderate-pressure plasma discharges. 1D self-consistent modeling predictions show agreement with experimental results within the estimated experimental error of 25%. The present results can be used to further the development of higher fidelity kinetic models while quantifying plasma-source characteristics.
The allowable strain in fibre reinforced polymers reinforcement is limited by design codes to avoid debonding. The near-surface mounted (NSM) reinforcement technique has been proven to produce better ...anchorage behaviour compared to externally bonded reinforcement solutions. However, NSM solutions do not always eliminate debonding issues, with concrete cover detachment (CCD) typically occurring in RC beams strengthened for flexure. This experimental study investigated the efficiency of side mounted (S) compared to bottom mounted (B) NSM bars to prevent CCD. The experimental results were compared to models available in the literature that predict the observed failure modes and the crack spacing in the NSM anchorage zone. Compared to B-NSM, the S-NSM solution was successful in avoiding brittle CCD failure and showed increased rotational capacity and energy dissipation at failure. Existing CCD debonding models were found to be conservative.
Nanopores have been explored as highly sensitive sensors for detection and rapid sequencing of single molecules of DNA. To sequence DNA with a nanopore requires that adenine (A), cytosine (C), ...thymine (T), and guanine (G) produce distinct current signals as they traverse the pore. Recently, we demonstrated that homopolymers of adenine, cytosine, and thymine immobilized in the nanopore protein α-hemolysin (αHL) produced distinct current blockades dependent on their chemical orientation. To probe the detection limit of αHL, we examined immobilized single strands of T40 DNA (polyT) with single base substitutions of A, C, and G at 12 positions on the strand occupying the stem region of αHL. We find blockade currents sensitive to base identity over most of these positions with the most sensitive region near the pore constriction. Adenine substitutions increase the measured blockade current to values intermediate to the polyT and polyA currents at a number of positions, while C substitutions increase the current to a level intermediate to polyT and polyC values in some positions, but decrease it below polyT in others. These changes in blockade current were also observed for G substitutions. These results indicate that total blockade currents measured in αHL arise from nucleotides at multiple locations and thus are not uniquely attributable to an individual base in a specific position, a finding consistent with a recently published study. The measurements of C and G substitutions also suggest that blockade current may be modulated through interactions between nucleotides and the pore interior at multiple sites in αHL.
Abstract Recirculating aquaculture systems (RAS) have become more attractive due to reduced water consumption and effluent discharge. However, intensification of production increases the risk of ...introducing pathogens at farming sites. The emergence of uncultivable pathogens and RAS pathobiome diversity shifts the traditional disease paradigm from “one pathogen, one disease” to complex multiple-pathogen disease cases. Piscine orthoreovirus genotype 3 (PRV-3) is an excellent example, as it is capable of inducing anemia and heart pathology resembling heart and skeletal muscle inflammation under experimental conditions, and is associated with increased mortality in association with other pathogens in the field. The aim of this study was to develop a method for detection of multiple pathogens and putative pathogens, as co-infections are common in aquaculture. To do this, in the pilot study, we mapped the pathobiome of RAS-farmed rainbow trout ( Oncorhynchus mykiss ) (commercial RAS, farm A) using both standard diagnostic methods and metabarcording (16S rRNA) to investigate the gill microbiome. During this study, we observed infections with multiple pathogens, and detected two putative gill pathogens Candidatus Branchiomonas cysticola and Candidatus Piscichlamydia salmonis, both of which have been linked with complex gill disease in Atlantic salmon ( Salmo salar ). Based on the pilot study, we developed and tested a high throughput qPCR (HT-qPCR) chip targeting 22 viral and bacterial pathogens and putative pathogens, followed by a surveillance of a fish cohort in a commercial RAS farm during production (farm B). Co-infection with PRV-3 and Ca. B. cysticola combined with stress inducing management practices may explain the severe disease outbreak observed (37% mortality). The time course study sets the base for a future screening scheme for disease prediction and addresses limitations of the method when testing environmental DNA/RNA.
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