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Discovery of a new natural product and a deactivation of a quorum sensing system by culturing a \u201cproducer\u201d bacterium with a heat-killed \u201cinducer\u201d culture
No full textHerein we describe a modified bacterial culture methodology as a tool to discover new natural products via supplementing actinomycete fermentation media with autoclaved cultures of \u201cinducer\u201d microbes. Using seven actinomycetes and four inducer microbes, we detected 28 metabolites that were induced in UHPLC-HRESIMS-based analysis of bacterial fermentations. Metabolomic analysis indicated that each inducer elicited a unique response from the actinomycetes and that some chemical responses were specific to each inducer-producer combination. Among these 28 metabolites, hydrazidomycin D, a new hydrazide-containing natural product was isolated from the pair Streptomyces sp. RKBH-B178 and Mycobacterium smegmatis. This result validated the effectiveness of the strategy in discovering new natural products. From the same set of induced metabolites, an in-depth investigation of a fermentation of Streptomyces sp. RKBH-B178 and autoclaved Pseudomonas aeruginosa led to the discovery of a glucuronidated analog of the pseudomonas quinolone signal (PQS). We demonstrated that RKBH-B178 is able to biotransform the P. aeruginosa quorum sensing molecules, 2-heptyl-4-quinolone (HHQ), and PQS to form PQS-GlcA. Further, PQS-GlcA was shown to have poor binding affinity to PqsR, the innate receptor of HHQ and PQS.Peer reviewed: YesNRC publication: Ye
Bell 412 system identification: comparing methods and tools
No full textOver the last decades system identification has become a standard method for developing rotorcraft models from flight test data. Using data from the Bell 412 Advanced Systems Research Aircraft (ASRA) helicopter operated by the National Research Council of Canada, different identification methods and tools are applied to a common database. The identified 6-DoF rigid-body models at one flight condition are compared in detail regarding eigenvalues and the match in both time and frequency domain. The development of a global model from point models that were identified at the different flight conditions is described. Finally, several possible extensions of the rigid-body models are investigated assessing corresponding improvement in model fidelity.Peer reviewed: NoNRC publication: Ye
Laser-additive repair of cast Ni\u2013Al\u2013bronze components
No full textTo emulate the refurbishment of service-damaged cast nickel aluminum bronze (NAB) components, a laser-additive repair process using NAB powder feed was developed. Process parameters were first optimized using Taguchi experimental design based on the lowest dilution ratio criterion. The dilution ratio was obtained from single weld beads deposited on flat substrates. Using the optimum process window developed on the flat substrates, the process parameters were further modified to deposit multiple weld beads in a grooved substrate, which was used to emulate remanufacturing of a service-damaged surface condition. Using the optimum laser-additive repair process developed, sound deposits with no cracks but some micropores at acceptable levels for the application, were successfully manufactured. The microstructure and microindentation hardness of the deposited specimen were evaluated in the as-deposited condition.Peer reviewed: YesNRC publication: N
Powder development and qualification for high-performance cold spray copper coatings on steel substrates
No full textThis paper presents the development work undertaken to tailor Cu powder size specifications to produce dense cold spray Cu coatings featuring strong adherence on steel substrates. Through review of historical data generated in the course of the development of Cu coatings for corrosion protection of Used (Nuclear) Fuel Containers, it was found that particle size distribution was particularly critical to meet application adhesion requirements of 60 MPa and prevent nozzle clogging during application; D01 and D90 were fixed at 5 and 60 \ub5m, respectively. The effect of powder size on coating microstructure and adhesion was further investigated with four Cu powder lots presenting different granulometries. The four lots were analyzed for composition, hardness, microstructure and morphology. Their in-flight particle velocities were measured using a coldspraymeter and the impact temperatures and velocities were simulated. Using fixed spraying conditions consisting of a He bond coat and a nitrogen buildup step, 3-4-mm-thick coatings were produced and tested for bond strength. Coating cross sections and fracture surfaces of selected coatings were examined. These trials confirmed that although the various powder sizes tested produced dense and sound coatings, tight control of particle size distributions was required to achieve optimal impact velocities that ensure deformation of the steel and good coating adhesion.Peer reviewed: YesNRC publication: Ye
Quantitation of selenomethionine in multivitamins and selenium supplements by high performance liquid chromatography inductively-coupled plasma mass spectrometry
No full textVITA-1 and VITB-1 multivitamin and mineral supplement candidate reference materials from the National Research Council Canada were analyzed for their total selenium and selenomethionine contents. Following a methanesulfonic acid reflux to extract selenomethionine from the selenized yeast in the multivitamins, analysis by high-performance liquid chromatography-inductively coupled plasma triple quadrupole mass spectrometry resulted in concentrations of 7.4 \ub1 3.0 \u3bcg SeMet g\u20131 and 16.4 \ub1 6.5 \u3bcg SeMet g 121 in VITA-1 and VITB-1, respectively. Twelve commercially available multivitamins and selenium supplements were analyzed following the same protocol. Seven of these were noted to contain 85\u2013115% of the selenium stated on the label; the others ranged from 5 to 147% of the claimed amount. Only one multivitamin contained selenomethionine at a concentration above the detection limit, but the amount found in the selenium supplements matched the label claims within a reasonable level of uncertainty. For comparison, two certified reference materials\u2014wheat gluten and egg powder, both certified for total selenium only\u2014were also examined and it was determined that selenomethionine accounted for 58% and 25% of the selenium in these food products, respectively.Peer reviewed: YesNRC publication: Ye
Failure modelling of a propulsion subsystem: unsupervised and semi-supervised approaches to anomaly detection
No full textPeer reviewed: YesNRC publication: Ye
Stretchable structure for a benchtop-scale morphed leading edge demonstration
No full textAdaptive structures and morphing aircraft technologies have generated much interest in the aerospace community, including regular sessions at AIAA conferences. However, due to the lack of suitable materials to make stretchable structures with loadbearing ability, relatively few works address the development of morphing wings that undergo substantial area change despite the advantage of doing so for the aerodynamic performance. At SciTech 2018 we first presented an approach to development of a stretchable skin based on carbon nanotube-polyurethane sheets with approximately 25 wt.% carbon nanotubes. In this paper we describe the production and properties of the nanocomposite skin, a complimentary support structure produced via structural optimization and 3D printing, and integration of these components along with a custom-designed actuation mechanism within a 25 cm wide, 200 cm long benchtop-scale morphing leading edge demonstration.Peer reviewed: YesNRC publication: Ye
GFRP-reinforced concrete slabs: fire resistance and design efficiency
No full textThickening concrete cover to obtain an adequate fire resistance lowers the efficiency of glass fiber\u2013reinforced polymer (GFRP) reinforcement and increases the cost relative to conventional steel reinforcement. This paper investigates the fire resistance of two full-scale GFRP-RC slabs with only 40 mm of clear concrete cover and 200 mm of unexposed (cool) anchor zone at the ends. Both slabs endured 3 h under the standard fire. The slabs were loaded with a sustained load, which caused a moment equal to 45% of their ultimate flexural strength. Emphasis was placed on studying the bond behavior of GFRP bars by comprehensively investigating temperature distributions particularly at the unexposed anchor zones at the ends of the slabs. The temperature reduces significantly in the unexposed zones, providing an adequate anchorage for the bars when almost the entire GFRP-to-concrete bond deteriorated in the exposed zone. The analysis of the experimental results showed that the increase in the tensile force in the GFRP bars during the standard fire is below 50% of the existing sustained force. A new model considers the bond degradation to predict the fire resistance of GFRP-reinforced slabs. The results enable an efficient, economic, and fire-safe application of GFRP reinforcement in concrete construction by reducing the concrete cover.Peer reviewed: YesNRC publication: Ye
Effect of Fe-rich intermetallics on tensile behavior of Al\u2013Cu 206 cast alloys at solid and near-solid states
No full textIron is one of the most common impurity elements in Al\u2013Cu 206 cast alloys as it often causes the precipitation of Fe-rich intermetallic phases during solidification due to its extremely low solid solubility in aluminum. The characteristics of the Fe-rich intermetallics, such as type, morphology, size, and distribution, have significant influences on the tensile behaviors of the Al alloys. In the present work, two Al\u2013Cu 206 cast alloys containing different types of Fe-rich intermetallics (dominated by either platelet \u3b2-Fe or Chinese script \u3b1-Fe) were cast and their tensile tests were performed at both solid (room temperature) and near-solid (2.8 vol. % liquid) states. It is found that the tensile properties in both solid and near-solid states are improved when the Fe-rich intermetallics change from platelet to Chinese script morphologies. During the solid-state tensile deformation, the failure occurs mainly along the platelet \u3b2-Fe intermetallics/Al matrix interface or within the Chinese script \u3b1-Fe particles. In the near-solid state, the alloy containing mainly Chinese script \u3b1-Fe is found to have more free flow paths for liquid feeding, leading to improved tensile properties. By contrast, the platelet \u3b2-Fe can cause the blockage of the liquid flow paths, leading to the degraded tensile properties and worsened susceptibility to hot-tearing.Peer reviewed: YesNRC publication: Ye