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Targeted capture of cpn60 gene fragments for PCR-independent microbial community profiling
No full textThis protocol describes the laboratory steps required to capture cpn60 gene fragments from microbial community DNA obtained from an environment of interest. This approach facilitates the determination of the taxonomic composition of a sample, providing information that spans all Domains of life (Bacteria, Eukarya, and Archaea). This method is independent of amplification biases associated with PCR, and provides a microbial community profile that is consistent with that generated using whole community shotgun sequencing, with substantially less sequencing effort required for the same community coverage. The protocol involves shearing the whole community genomic DNA by sonication, adding Illumina index primers, then hybridizing the sheared DNA to biotinylated RNA probes that correspond to the entire cpn60 reference database. Hybrids are selected using magnetic streptavidin beads, washed, and sequenced using an Illumina MiSeq platform. The protocol involves approximately five hours of hands-on time per sample over two days, along with a 24 hour hybridization step. In this protocol we describe the major changes we have implemented using the manufacturer\u2019s recommendations as a starting point. We also provide tips and expected results.Peer reviewed: YesNRC publication: Ye
A bibliometric analysis of observatory publications 2011-2015
No full textBibliometrics are increasingly used as metrics to measure the performance of individuals, institutions and countries. Refereed publications are the primary output of modern observatories. In this paper, I use bibliometric techniques to examine the performance of astronomical observatories.Peer reviewed: YesNRC publication: Ye
A comparison of strong and weak coupling schemes for computational aeroelasticity in OpenFOAM
No full textTwo coupling schemes for fluid-structure interaction using the OpenFOAM structural solver sixDoF Rigid Body Motion are developed. The first scheme is developed by modifying the baseline leapfrog weak coupling scheme to minimize the lag between the fluid and structural solvers. The second is a strong coupling scheme based on the Crank-Nicolson method. The two newly implemented schemes and the baseline are compared through the aeroelastic simulation of a NACA 64A010 airfoil and the Benchmark Supercritical Wing. The aeroelastic solutions obtained using the newly implemented schemes exhibit significantly lower sensitivity to changes in time step size compared to the baseline weak coupling scheme. The modified weak coupling and strong coupling schemes perform comparably for the cases studied.Peer reviewed: YesNRC publication: Ye
An ALMA 3 mm continuum census of Westerlund 1
No full textMassive stars play an important role in both cluster and galactic evolution and the rate at which they lose mass is a key driver of both their own evolution and their interaction with the environment up to and including their terminal SNe explosions. Young massive clusters provide an ideal opportunity to study a co-eval population of massive stars, where both their individual properties and the interaction with their environment can be studied in detail. We aim to study the constituent stars of the Galactic cluster Westerlund 1 in order to determine mass-loss rates for the diverse post-main sequence population of massive stars. To accomplish this we made 3mm continuum observations with the Atacama Large Millimetre/submillimetre Array. We detected emission from 50 stars in Westerlund 1, comprising all 21 Wolf-Rayets within the field of view, plus eight cool and 21 OB super-/hypergiants. Emission nebulae were associated with a number of the cool hypergiants while, unexpectedly, a number of hot stars also appear spatially resolved. We were able to measure the mass-loss rates for a unique population of massive post-main sequence stars at every stage of evolution, confirming a significant increase as stars transitioned from OB supergiant to WR states via LBV and/or cool hypergiant phases. Fortuitously, the range of spectral types exhibited by the OB supergiants provides a critical test of radiatively-driven wind theory and in particular the reality of the bi-stability jump. The extreme mass-loss rate inferred for the interacting binary Wd1-9 in comparison to other cluster members confirmed the key role binarity plays in massive stellar evolution. The presence of compact nebulae around a number of OB and WR stars is unexpected; by analogy to the cool super-/hypergiants we attribute this to confinement and sculpting of the stellar wind via interaction with the intra-cluster medium/wind. Given the morphologies of core collapse SNe depend on the nature of the pre-explosion circumstellar environment, if this hypothesis is correct then the properties of the explosion depend not just on the progenitor, but also the environment in which it is located.Peer reviewed: YesNRC publication: Ye
An examination of the besetting of the MV Berge Atlantic
No full textA detailed account of the besetting and break-out of the MV Berge Atlantic in the Gulf of St. Lawrence in 2014 is presented. Field observations indicate that besetting occurred with the absence of significant ice pressure, and may have been triggered by ice ridging. An ice dynamics model was used to reproduce the evolution of ice conditions in the vicinity of the beset vessel. The results show that appropriate initialization of ridge distribution is needed for accurate evaluation of the risk of besetting.Peer reviewed: YesNRC publication: Ye
An improved secondary reflector for DVA-2 radio telescope: a case study on application of structural optimization technique
No full textDish Verification Antennae (DVA)\u20131 demonstrates excellent performance at L-band and can operate reasonably up to 10 GHz. However, with recent technological advances, there is a push towards the development of high frequency radio telescopes up to Q-Band and more. As an attempt to demonstrate the capabilities of the composite radio telescopes at higher frequency range (up to Q-Band), a DVA\u20132 is currently under construction. In this article the authors will elaborate the design path towards the improved carbon based secondary dish support structure (SDSS) for the DVA\u20132. In DVA\u20131, the secondary support structure was directly connected to the secondary reflector at four points. At various gravity loads, it is observed in finite element analysis (FEA) that the distortion from the feed platform and adjacent structures are directly transferred into the secondary rim and eventually on to the surface. To separate the effects, a ring made out of carbon composite was placed between the support structure and the secondary reflector. To investigate the size of the ring and especially the layup of the composite, a topology optimization and free-size optimization was performed. A further improvement was achieved by carefully investigating the deformations in the ring and locally stiffening the connection points of the landing tubes on the ring. All these changes in the SDSS resulted in a 96% reduction in RMS residual error for the worst case condition at 15\ub0 elevation angle. A combination of careful analyses and application of optimization techniques was paramount to achieve 50GHz performance.Peer reviewed: YesNRC publication: Ye
An investigation of the mechanisms causing large-amplitude wind-induced vibrations in stay cables using unsteady surface pressure measurements
No full textDry galloping has been observed on in-service bridges and has been reproduced in several wind tunnel experiments of inclined stay cables. In certain cases, the large-amplitude vibrations caused by dry galloping could not be mitigated with damping levels specified by the Post Tensioning Institute (PTI). Wind tunnel investigations were conducted for IHI Corporation on a 1:1 scale sectional model of an inclined bridge stay cable in the 3\u202fm\u202f
7\u202f6\u202fm Wind Tunnel at the National Research Council Canada in 2015. The purpose of the investigation was to reproduce large amplitude cable galloping, which had been observed at an existing cable-stayed bridge in Japan. The experiment was designed to investigate the influence of different damping levels and the ability of a 5\u202fmm-diameter helical fillet to mitigate dry cable vibrations. The current work identified several important factors that contributed to dry galloping and large-amplitude cable motions. It was shown that the physical mechanisms leading to the onset of large-amplitude motion in the critical and supercritical Reynolds number regimes are distinct. In the critical Reynolds number regime, the drop in drag, increase in lift, and fluctuations in the laminar separation bubbles along the cable destabilize the low pressure lobes, allowing the changes in pressure along the cable to become synchronized with the cable motion in a highly-correlated manner. This type of galloping could not be mitigated with damping greater than that required by the PTI. At high Reynolds numbers, the boundary layer state changed and was associated with the upstream movement of the separation point and an asymmetric pressure distribution, K\ue1rm\ue1n vortex shedding re-emerged and appeared to combine with low-frequency variations to induce large-amplitude motion. The large-amplitude motion at high Reynolds numbers could be mitigated with additional damping.Peer reviewed: YesNRC publication: Ye
Cascaded Mach\u2013Zehnder architectures for photonic integrated delay lines
No full textA continuously tunable integrated optical delay line architecture with large bandwidth and bandwidth-delay product is proposed and demonstrated. The non-resonant delay line is based on cascaded Mach-Zehnder interferometers with tunable couplers. The device is operated with a single control signal and outperforms the common ring-resonator-based delay lines in terms of bandwidth-delay product. A device with a delay tuning range of 124 ps is experimentally demonstrated over a transmission bandwidth of 4.5 GHz.Peer reviewed: YesNRC publication: Ye
Determination of sulfur and sulfate half-ester content in cellulose nanocrystals: an interlaboratory comparison
No full textCharged functional groups on the surface of cellulose nanocrystals (CNCs) are important for controlling the colloidal stability of suspensions and the interaction of the material with its environment. Quantification of surface groups is therefore an important metric for reproducible production of this nanomaterial. Here we report the results of an interlaboratory comparison (ILC) with twelve participants piloted by National Research Council Canada (NRC) that evaluated two methods for determining the sulfur content for an NRC reference material (CNCD-1) produced from CNCs extracted by sulfuric acid hydrolysis of wood pulp. Inductively coupled plasma-optical emission spectroscopy (ICP-OES) was used to measure the total sulfur content of CNCs after microwave assisted digestion in strong acid. Conductometric titration quantified the negatively charged sulfate half-ester groups on the CNC surface after dialysis and protonation using ion exchange resin. The data was analyzed with an ASTM method that employs h and k statistics to identify data sets for which the laboratory mean or standard deviation show excessive variation from the overall mean or standard deviation and the NIST consensus builder (NICOB) engine using the DerSimonian\u2013Laird meta-analysis to determine a consensus estimate of the mean and its associated measurement uncertainty. The consensus estimates\u2009\u2009\ub1\u2009\u2009uncertainty for total sulfur and sulfate half ester content were (8771\u2009\u2009\ub1\u2009\u200994) mg kg 121 and (252.0\u2009\u2009\ub1\u2009\u20098.2) mmol kg 121, respectively. Neither approach identified any outliers in the data sets and the consensus estimates were in agreement with values obtained during certification of the reference material. The results confirmed that the difference between the sulfur content measured by conductometric titration and ICP-OES is larger than the combined 95% expanded uncertainties. The higher sulfur content measured by ICP-OES may reflect the presence of sulfur impurities that are not detected by titration. Overall the ILC provides validation for the protocols for the two methods and indicates that both are reasonably tolerant of small variations from the protocol. A more reliable method of assessing the titration endpoint and a quality control (QC) sample were identified as potential improvements to reduce variability for the conductometric titration.Peer reviewed: YesNRC publication: Ye
Energy performance based anomaly detection in non-residential buildings using symbolic aggregate approximation
No full textBuilding system faults in commercial and office buildings can result in a reduced occupant comfort and increased utility bills. Energy performance-based anomaly detection helps operators efficiently identify faults. In this work, a data-driven method for anomaly detection is presented. Using a symbolic aggregate method, the weekly energy demand profiles are statistically quantised and labeled to determine normal and abnormal building behaviours. A case study with three federal office buildings has been conducted to demonstrate the proposed method. The resulting technology provides building operators with easily-interpreted and actionable information for optimised building performance.Peer reviewed: YesNRC publication: Ye