National Research Council Canada
Recent publications
We consider the problem of learning a neural network classifier. Under the information bottleneck (IB) principle, we associate with this classification problem a representation learning problem, which we call “IB learning”. We show that IB learning is, in fact, equivalent to a special class of the quantization problem. The classical results in rate-distortion theory then suggest that IB learning can benefit from a “vector quantization” approach, namely, simultaneously learning the representations of multiple input objects. Such an approach assisted with some variational techniques, result in a novel learning framework, “Aggregated Learning”, for classification with neural network models. In this framework, several objects are jointly classified by a single neural network. The effectiveness of this framework is verified through extensive experiments on standard image recognition and text classification tasks.
Ciguatera poisoning (CP) is endemic to several subtropical and tropical regions and is caused by the consumption of fish contaminated with ciguatoxins (CTXs). The recent discovery of Caribbean CTXs (C-CTXs) in Gambierdiscus spp. isolated from the Caribbean resulted in the identification of a precursor analogue, C-CTX5, that is reduced into C-CTX1. C-CTX5 has two reducible sites, a ketone at C-3 and hemiketal at C-56. Chemical reductions of C-CTX5 into C-CTX3/4 resulted in two peaks in the LC−HRMS chromatograms with a ratio that differed markedly from that observed in fish extracts and the reduction of C-CTX1 isolated from fish. Reduction of C-CTX5 should have produced four diastereoisomers of C-CTX3/4, prompting a more detailed study of the reduction products. LC–HRMS with a slow gradient was used to separate and detect the four stereoisomers of C-CTX3/4, and to determine the distribution of these analogues in naturally contaminated fish tissues and following chemical reduction of isolated analogues. The results showed that in naturally contaminated fish tissues C-CTX1/2 is a mixture of two diastereoisomers at C-3 and that C-CTX3/4 is a mixture of two pairs of diastereoisomers at C-3 and C-56. The data suggests that there is variability in the enzymatic reduction at C-3 and C-56 of C-CTXs in reef fish, leading to variations in the ratios of the four stereoisomers. Based on these findings, a naming convention for C-CTXs is proposed which aligns with that used for Pacific CTX congeners and will aid in the identification of the structure and stereochemistry of the different CTX analogues.
The goal of this study is to provide a benchmark for the use of Monte Carlo simulation when applied to coincidence summing corrections. The examples are based on simple geometries: two types of germanium detectors and four kinds of sources, to mimic eight typical measurement conditions. The coincidence corrective factors are computed for four radionuclides. The exercise input files and calculation results with practical recommendations are made available for new users on a dedicated webpage.
Site-specific carbon isotope ratio measurements by quantitative 13 C NMR (13 C-qNMR), Orbitrap-MS, and GC-IRMS offer a new dimension to conventional bulk carbon isotope ratio measurements used in food provenance, forensics, and a number of other applications. While the site-specific measurements of carbon isotope ratios in vanillin by 13 C-qNMR or Orbitrap-MS are powerful new tools in food analysis, there are a limited number of studies regarding the validity of these measurement results. Here we present carbon site-specific measurements of vanillin by GC-IRMS and 13 C-qNMR for methoxy carbon. Carbon isotope delta (δ 13 C) values obtained by these different measurement approaches demonstrate remarkable agreement; in five vanillin samples whose bulk δ 13 C values ranged from −31‰ to −26‰, their δ 13 C values of the methoxy carbon ranged from −62.4‰ to −30.6‰, yet the difference between the results of the two analytical approaches was within ±0.6‰. While the GC-IRMS approach afforded up to 9-fold lower uncertainties and required 100-fold less sample compared to the 13 C-qNMR, the 13 C-qNMR is able to assign δ 13 C values to all carbon atoms in the molecule, not just the cleavable methoxy group.
When verifying the validity of the exponential-decay law through 137 precise decay rate measurement series at various nuclear laboratories, minor violations have been observed in the shape of annual cycles in the residuals with different amplitudes and phase shifts. The timing and amplitude of these deviations have been compared with local weather data and it appears that ambient humidity is highly correlated with the observed instabilities in these radioactivity measurements. In fact, when compensating the residuals for a linear relationship with absolute humidity in air, most of the annual cycles are no longer statistically significant. As a result, the validity of the exponential-decay law can now be demonstrated with even higher fidelity.
Carboxylated cellulose nanocrystals (cCNCs) were blended with high‐quality commercial latex to enhance key pressure‐sensitive adhesive (PSA) properties: tack, peel strength, and shear adhesion. Initially, a 2 5–1 fractional factorial design was used to evaluate the effect of five factors: cCNC type (never‐dried vs. dried re‐dispersed), the use of sonication to disperse the cCNC, cCNC loading, blend temperature, and mixing speed. The regression analysis identified optimal blend conditions and the three most significant factors. It was found that increasing mixing speed had the strongest positive impact on all three PSA properties. A subsequent design of experiments looked at using a different mixing system—a homogenizer—and the data were viewed relative to the mixing power. Further increase in mixing beyond the original design framework led to increase in shear adhesion but decreased tack and peel strength. Nevertheless, in all cases, the PSA properties of the blended latexes exceeded that of the base‐case latex without cCNCs. The second factor of importance was the cCNC loading. The blending of cCNCs at levels beginning at 0.5 phm (parts per hundred parts monomer) led to the simultaneous improvement in all three PSA properties compared to the base‐case latex. The 1 phm level appeared to provide the best impact on the PSA properties. Finally, the need to sonicate the cCNCs dispersions before blending was significant. The results were further supported by rheological measurements, which demonstrated significant increase in viscosity with cCNC addition. This study clearly demonstrates the effectiveness of cCNC blending to improve all PSA properties simultaneously and provides practical insights for industrial‐scale application.
Background and objectives There has been a significant increase in the use of fermentation for protein modification by the food industry. This research aimed to investigate the use of solid‐state fermentation (SSF) by Aspergillus oryzae NRRL 5590 on pea and navy bean protein isolates (PPI and NBPI, respectively) to enhance their physicochemical and functional properties. Findings The impact of fermentation was more profound on PPI than NBPI with a higher degree of hydrolysis achieved for the former (9.3% versus 4.4%). Fermented PPI had significantly increased protein content, surface charge and hydrophobicity, solubility, and foaming properties, but decreased emulsion stability. For NBPI, modifications were only observed for surface hydrophobicity and water hydration capacity (WHC), which both increased after fermentation. Overall, navy bean proteins were less susceptible to protein hydrolysis than pea proteins upon fermentation, possibly due to the phaseolin protein in navy bean. Conclusions In summary, fermentation may be used to enhance the solubility and foaming properties of PPI and WHC of NBPI for their use as ingredients in applications where such higher functionalities are favorable. Significance and novelty The results provide insights into pulse protein modification by bioprocessing, specifically fermentation, and opportunities for potential value‐added applications for pea and navy bean proteins. This article is protected by copyright. All rights reserved.
The mechanical behaviour of wood light-frame shearwalls is difficult to explain unless system-level performance is taken into account. Although the behaviour of wood light-frame shearwalls with wood structural panels is consistent with and represented by the behaviour of the panel to framing nail joints, comprehensive seismic evaluation guidelines for Canadian practice are currently lacking. This paper presents a critical review of the available literature on performance-based seismic evaluation of wood light-frame buildings through nonlinear analysis approach. To verify the applicability of these standards in Canada, the procedure outlined in these documents are compared to available experimental testing. Nonlinear pushover analysis is performed on two representative wood light-frame buildings in Montréal and Vancouver. Results are compared, and further discussion is provided on the adequacy of each document to Canadian practice.
In this study, W0.4MoNb1.3TaTiZrX (X = 0, 0.5, 0.7, and 1.0) alloys were designed using empirical design parameters to expand upon an existing refractory high entropy alloy with the purpose of examining the microstructural effects of Zr addition on the alloy system. The four designed alloys were vacuum arc cast and were then subjected hot isostatic pressing prior to a detailed metallurgical and hardness evaluation. The W0.4MoNb1.3TaTiZrX alloys formed a primary BCC solid solution matrix, with the W0.4MoNb1.3TaTiZr0 alloy being a single-phase BCC solid solution in both the as-cast condition and following hot isostatic pressing. The addition of Zr in the as-cast W0.4MoNb1.3TaTiZrX alloy resulted in an increasing volume fraction of a secondary interdendritic BCC phase, within which a eutectic/eutectoid Zr-rich HCP phase formed proportionally within this BCC region as the Zr content of the alloy increased. Following hot isostatic pressing, the secondary BCC and HCP phases transformed into a Zr/Ti rich α-HCP phase, leaving a BCC + HCP phase composition in the Zr0.5–1.0 alloys. The microhardness of the W0.4MoNb1.3TaTiZrX alloys also increased with increasing Zr content in both heat treatment conditions. The formation of secondary phases is attributed to insolubilities between alloying elements which empirical design parameters failed to predict.
Modes of propagation through an optical system are generally defined as the eigensolutions of the wave equation in the system. When propagation occurs through complicated or highly scattering media, however, modes are better identified as the best orthogonal communication channels to send information between sets of input and output apertures. Here we determine the optimal bidirectional orthogonal communication channels through arbitrary and scattering optical systems using photonic processors. The processors consist of meshes of electrically tuneable Mach–Zehnder interferometers in silicon photonics. The meshes can configure themselves based on simple power maximization or minimization algorithms, without external calculations or calibration or any prior knowledge of the optical system. The identification of the communication mode channels corresponds to a singular value decomposition of the entire optical system, autonomously performed by the photonic processors. We observe crosstalk below –30 dB between the optimized channels even in the presence of distorting masks or partial obstructions. In these cases, although the beams bear little resemblance to conventional mode families, they still show orthogonality. These findings offer potential for applications in multimode optical communication systems, promising efficient channel identification, adaptability to dynamic media and robustness against environmental challenges.
An overview of the additive/subtractive hybrid manufacturing (ASHM) research on three heat resisting materials – 18Ni-300 maraging steel, 316L stainless steel, and Inconel 718 (hereinafter 18Ni-300, 316L and IN718) – is provided to bridge key knowledge gaps and establish the respective process-microstructure-property relationships. The results examine validating the final surface roughness properties in the as-built and machined conditions in terms of the linear and areal parameters. Microscopic observations are also detailed to identify the influence of dry machining intermittent passes and/or laser conditions on microstructural features, as well as the bulk density. Mechanical stability assessment involved hardness measurement and tensile testing to evaluate the mechanical response of the materials built by in-envelope ASHM.
Mushrooms are considered a valuable food source due to their high protein and fibre and low fat content, among the other health benefits of their consumption. Selenium is an essential nutrient and is renowned for its chemo-preventative properties. In this study, batches of selenium-enriched Lingzhi mushrooms were prepared by growing mycelium and fruit in substrates containing various concentrations of sodium selenite. The mushroom fruit accumulated low levels of selenium with selenomethionine being the most abundant form in all enriched samples. Conversely, the mycelium showed significant selenium accumulation but relatively low proportions of selenomethionine. The red colour of the selenium-enriched mycelia indicated the probable presence of selenium nanoparticles, which was confirmed by single-particle inductively coupled plasma-mass spectrometry. Mean particle diameters of 90–120 nm were observed, with size distributions of 60–250 nm. Additional analysis with transmission electron microscopy confirmed this size distribution and showed that the biogenic selenium nanoparticles were roughly spherical in shape and contained elemental selenium.
Wood pellets have gained global attention due to their economic availability and increasing demand for bioenergy as part of sustainable energy solutions. Management of the wood pellet supply chains, from feedstock harvesting to bioenergy conversion, is critical to ensure competitiveness in the energy markets. In this regard, wood pellets supply chain coordination can play a strategic role in enhancing the efficiency and reliability of bioenergy generation. This study proposes a contract-based coordination mechanism for wood pellet supply chains and compares its performance in alternative centralized and decentralized decision-making structures. A bi-level nonlinear game-theoretic approach with two economic and environmental objective functions is developed. It utilizes the concept of life cycle assessment in a Stackelberg leader–follower game to obtain the bioenergy equilibrium solutions. Further, this study examines the case of wood pellet supply chains in three remote Canadian communities. The aim is to showcase the practicality and significance of the proposed approach and interpret the findings. By focusing on these communities, the crucial role of supply chain coordination in fostering sustainable development, particularly, in the context of bioenergy generation is emphasized. The study colludes by advocating a number of avenues for future research.
The gas-phase technique of noncollinear two-color excitation is adapted to study extreme-ultraviolet high-order harmonic generation (HHG) in magnesium oxide. We observe high-order wave-mixing pathways with brightness comparable to that of the single-color HHG. Simulations reveal that the efficiencies are dominated by the microscopic physics as opposed to macroscopic effects. Building on previous work, we develop a general analytic theory of high-order wave mixing that explains our observations and demonstrates how a perturbative nonlinear optical framework emerges form the interaction between the weak field and the laser-dressed state of the crystal in the strong-field approximation. The theory outlines a photon-mixing picture of high-order wave mixing and connects the strong asymmetry between sum- and difference-frequency pathways to the cutoff in the HHG spectrum. Our work establishes the potential of high-order wave mixing as a probe of the microscopic attosecond physics in solids and points to new opportunities in solid-state strong-field photonics.
Bridge managers need to generate a complete overview of required interventions, possession windows and the likely costs 10-20 years ahead of execution. These, even if approximate, help ensure stable train schedules. With the increasing amount of available data and the increasing desire to exploit digitalisation to improve decision-making, bridge managers are perfectly poised to make or improve these estimates by moving on from current qualitative methods. This paper proposes a way in the current climate to use digitalisation and existing data to generate approximate overviews of required interventions 10-20 years ahead of time, including estimates of component-level bridge interventions, possession windows, likely costs, and the increases in failure risks if interventions are postponed. A demonstration is done on 41 bridges of a 25 km railway network in Switzerland. It is argued that the algorithm generates a more complete and consistent overview of component-level interventions, possession windows, and costs compared to the current qualitative methods. Additionally, the algorithm generates a solid basis for the initiation of detailed investigations of the bridges by engineering offices, i.e., the investigations that result in the information required for scheduling an intervention, as well as estimating the type of intervention and track possession are required.
Real-time probing of electrons can uncover intricate relaxation mechanisms and many-body interactions in strongly correlated materials. Here, we introduce time, momentum, and energy resolved pump-probe tunneling spectroscopy (Tr-MERTS). The method allows the injection of electrons at a particular energy and observation of their subsequent decay in energy-momentum space. Using Tr-MERTS, we visualize electronic decay processes, with lifetimes from tens of nanoseconds to tens of microseconds, in Landau levels formed in a GaAs quantum well. Although most observed features agree with simple energy-relaxation, we discovered a splitting in the nonequilibrium energy spectrum in the vicinity of a ferromagnetic state. An exact diagonalization study suggests that the splitting arises from a maximally spin-polarized state with higher energy than a conventional equilibrium skyrmion. Furthermore, we observe time-dependent relaxation of the splitting, which we attribute to single-flipped spins forming skyrmions. These results establish Tr-MERTS as a powerful tool for studying the properties of a 2DES beyond equilibrium.
Isotopic measurements provide valuable information about the origin of greenhouse gases — as carbon dioxide levels increase, there is a corresponding shift towards lighter isotopic composition similar to that of fossil fuels. Detecting such isotopic shifts, however, requires extremely precise measurements, which must also be globally reproducible in order to make reliable policy decisions. This feature article outlines the collective search for the ideal standard for carbon isotope measurements since the 1950s. This tragicomedy of errors, if you wish, has strengthened the reliability of today’s measurements and has taken us from fictional oceans, to toilet seat marbles, and complex mathematical conventions that separate data from reliable results.
Institution pages aggregate content on ResearchGate related to an institution. The members listed on this page have self-identified as being affiliated with this institution. Publications listed on this page were identified by our algorithms as relating to this institution. This page was not created or approved by the institution. If you represent an institution and have questions about these pages or wish to report inaccurate content, you can contact us here.
1,497 members
Devendra Hiraman Dusane
  • Aquatic and Crop Resource Development Research Area
Pankaj Bhowmik
  • Aquatic and Crop Resource Development (ACRD)
Scott McComb
  • Human Health and Therapeutics, Vaccines Division
Miroslava Cuperlovic-Culf
  • Information and Communications Technologies
Alex Chun-te Ko
  • Medical Devices Research Area
100 Sussex Dr, K1A 0R6, Ottawa, ON, Canada
Head of institution
National Research Council of Canada