57949 research outputs found
Sort by
Capillary electrophoresis\u2013tandem mass spectrometry for multiclass analysis of polar marine toxins
No full textPolar marine toxins are more challenging to analyze by mass spectrometry-based methods than lipophilic marine toxins, which are now routinely measured in shellfish by multiclass reversed-phase liquid chromatography\u2013tandem mass spectrometry (MS/MS) methods. Capillary electrophoresis (CE)\u2013MS/MS is a technique that is well suited for the analysis of polar marine toxins, and has the potential of providing very high resolution separation. Here, we present a CE\u2013MS/MS method developed, with use of a custom-built interface, for the sensitive multiclass analysis of paralytic shellfish toxins, tetrodotoxins, and domoic acid in seafood. A novel, highly acidic background electrolyte (5 M formic acid) was designed to maximize protonation of analytes and to allow a high degree of sample stacking to improve the limits of detection. The method was applied to a wide range of regulated and less common toxin analogues, and exhibited a high degree of selectivity between toxin isomers and matrix interference. The limits of detection in mussel tissue were 0.0052 mg/kg for tetrodotoxins, 0.160 mg/kg for domoic acid, and between 0.0018 and 0.120 mg/kg for paralytic shellfish toxins, all of which showed good linearity. Minimal ionization suppression was observed when the response from neat and mussel-matrix-matched standards was corrected with multiple internal standards. Analysis of shellfish matrix reference materials and spiked samples demonstrated good accuracy and precision. Finally, the method was transferred to a commercial CE\u2013MS/MS system to demonstrate its widespread applicability for use in both R & D and routine regulatory settings. The approach of using a highly acidic background electrolyte is of broad interest, and can be considered generally applicable to simultaneous analysis of other classes of small, polar molecules with differing pKa values.Peer reviewed: YesNRC publication: Ye
Selenium analysis in waters. Part 2: Speciation methods
No full textIn aquatic ecosystems, there is often no correlation between the total concentration of selenium present in the water column and the toxic effects observed in that environment. This is due, in part, to the variation in the bioavailability of different selenium species to organisms at the base of the aquatic food chain. The first part of this review (Kumkrong et al., 2018) discusses regulatory framework and standard methodologies for selenium analysis in waters. In this second article, we are reviewing the state of speciation analysis and importance of speciation data for decision makers in industry and regulators. We look in detail at fractionation methods for speciation, including the popular selective sequential hydride generation. We examine advantages and limitations of these methods, in terms of achievable detection limits and interferences from other matrix species, as well as the potential to over- or under-estimate operationally-defined fractions based on the various conversion steps involved in fractionation processes. Additionally, we discuss methods of discrete speciation (through separation methods), their importance in analyzing individual selenium species, difficulties associated with their implementation, as well as ways to overcome these difficulties. We also provide a brief overview of biological treatment methods for the remediation of selenium-contaminated waters. We discuss the importance of selenium speciation in the application of these methods and their potential to actually increase the bioavailability of selenium despite decreasing its total waterborne concentration.Peer reviewed: YesNRC publication: Ye
Real-time spectral characterization of a photon pair source using a chirped supercontinuum seed
No full textPhoton pair sources have wide ranging applications in a variety of quantum photonic experiments and protocols. Many of these protocols require well controlled spectral correlations between the two output photons. However, due to low cross-sections, measuring the joint spectral properties of photon pair sources has historically been a challenging and time-consuming task. Here, we present an approach for the real-time measurement of the joint spectral properties of a fiber-based four wave mixing source. We seed the four wave mixing process using a broadband chirped pulse, studying the stimulated process to extract information regarding the spontaneous process. In addition, we compare stimulated emission measurements with the spontaneous process to confirm the technique\u2019s validity. Joint spectral measurements have taken many hours historically and several minutes with recent techniques. Here, measurements have been demonstrated in 5\u201330 s depending on resolution, offering substantial improvement. Additional benefits of this approach include flexible resolution, large measurement bandwidth, and reduced experimental overhead.Peer reviewed: YesNRC publication: Ye
Recent advancements in the development of bifunctional electrocatalysts for oxygen electrodes in unitized regenerative fuel cells (URFCs)
No full textAn ever-increasing energy demand has stimulated intense research into electrochemical technologies for both energy storage and conversion such as unitized regenerative fuel cells (URFCs). Due to its high efficiency, low cost, and low environmental impact, the URFC, which combines a polymer electrolyte membrane fuel cell (PEMFC) with a polymer electrolyte water electrolyzer (PEWE), has been regarded as an important energy technology that can offer new opportunities to not only further reduce investment costs but also to open doors to the mass production of domestic applications. Despite this, URFCs still have to be further improved and optimized to reach a level of maturity of both fuel cells and electrolyzers in terms of energy efficiency and long-term performance. Currently, the major challenge of URFC technology has been the insufficient performance of the bifunctional electrocatalyst. Based on the most recent research trends and progresses of bifunctional oxygen catalyst materials, this review will provide a systematic introduction and a comprehensive assessment of various bifunctional oxygen catalysts; their science and technology, including material selection, synthesis, and characterization, as well as their applications in URFCs. This review aims to correlate the physicochemical characteristics of URFCs with the catalytic activity/stability of these materials.Peer reviewed: YesNRC publication: Ye
Regenerable urchin-like Fe3O4@PDA-Ag hollow microspheres as catalyst and adsorbent for enhanced removal of organic dyes
No full textIn this work, novel urchin-like Fe3O4@polydopamine (PDA)-Ag hollow microspheres have been prepared via a facile synthesis method by in situ reduction and growth of Ag nanoparticles on mussel-inspired PDA layers coated on Fe3O4 hollow cores. The catalytic reduction efficiency and adsorption performance of the as-prepared urchin-like Fe3O4@polydopamine (PDA)-Ag hollow microspheres for model organic dyes (i.e., methylene blue and rhodamine B) under varying pH condition have been systematically investigated, which are demonstrated to be significantly enhanced as compared to that of spherical (relatively smooth) solid Fe3O4@PDA-Ag microspheres. The as-prepared urchin-like Fe3O4@PDA-Ag hollow microspheres show high reusability, easy separability, and fast regeneration ability, with no obvious drop in the catalytic and adsorption efficiency after cyclic reuse. The versatile PDA coatings on the urchin-like microspheres allow further surface functionalization for development of multifunctional catalyst and adsorbent materials. This work provides a very useful and facile methodology for synthesizing and tuning the urchin-like morphology of Fe3O4@PDA-Ag microspheres, with great potential applications in catalysis and wastewater treatment.Peer reviewed: YesNRC publication: Ye
Relationship between QTL for grain shape, grain weight, test weight, milling yield, and plant height in the spring wheat cross RL4452/\u2018AC Domain\u2019
No full textKernel morphology characteristics of wheat are complex and quantitatively inherited. A doubled haploid (DH) population of the cross RL4452/\u2018AC Domain\u2019 was used to study the genetic basis of seed shape. Quantitative trait loci (QTL) analyses were conducted on a total of 18 traits: 14 grain shape traits, flour yield (Fyd), and three agronomic traits (Plant height [Plht], 1000 Grain weight [Gwt], Test weight [Twt]), using data from trial locations at Glenlea, Brandon, and Morden in Manitoba, Canada, between 1999 and 2004. Kernel shape was studied through digital image analysis with an Acurum\uae grain analyzer. Plht, Gwt, Twt, Fyd, and grain shape QTL were correlated with each other and QTL analysis revealed that QTL for these traits often mapped to the same genetic locations. The most significant QTL for the grain shape traits were located on chromosomes 4B and 4D, each accounting for up to 24.4% and 53.3% of the total phenotypic variation, respectively. In addition, the most significant QTL for Plht, Gwt, and Twt were all detected on chromosome 4D at the Rht-D1 locus. Rht-D1b decreased Plht, Gwt, Twt, and kernel width relative to the Rht-D1a allele. A narrow genetic interval on chromosome 4B contained significant QTL for grain shape, Gwt, and Plht. The \u2018AC Domain\u2019 allele reduced Plht, Gwt, kernel length and width traits, but had no detectable effect on Twt. The data indicated that this variation was inconsistent with segregation at Rht-B1. Numerous QTL were identified that control these traits in this population.Peer reviewed: YesNRC publication: Ye
Stochastic process design kits for photonic circuits based on polynomial chaos augmented macro-modelling
No full textFabrication tolerances can significantly degrade the performance of fabricated photonic circuits and process yield. It is essential to include these stochastic uncertainties in the design phase in order to predict the statistical behaviour of a device before the final fabrication. This paper presents a method to build a novel class of stochastic-based building blocks for the preparation of Process Design Kits for the analysis and design of photonic circuits. The proposed design kits directly store the information on the stochastic behaviour of each building block in the form of a generalized-polynomial-chaos-based augmented macro-model obtained by properly exploiting stochastic collocation and Galerkin methods. Using these macro-models, only a single deterministic simulation is required to compute the stochastic moments of any arbitrary photonic circuit, without the need of running a large number of time-consuming circuit simulations thereby dramatically improving simulation efficiency. The effectiveness of the proposed approach is verified by means of classical photonic circuit examples with multiple uncertain variables.Peer reviewed: YesNRC publication: Ye
Evaluation of the communication performance of the C4 chemical, biological, radiological and nuclear mask
No full textThe Canadian Armed Forces (CAF) are using chemical, biological, radiological and nuclear (CBRN) general service respirators (GSRs) to defend against CBRN threats and hazards to protect personnel and ensure that they can safely and successfully carry out missions. The CBRN GSR currently in use by the CAF is the C4 respirator. The National Research Council Canada assessed the communication performance of the C4 respirator. This report presents the results of the performance test. The method for assessing the communication performance used in this study was the NIOSH standard test procedure TEB-CBRN-APR-STP-0313 [1]. Other methods exist to evaluate the communication performance of respirators, but historically the NIOSH standard test procedure has been used. This report details the implementation and results of the tests conducted at the National Research Council Canada, following the NIOSH standard test procedure.Peer reviewed: NoNRC publication: Ye
Approach for assessing the climate resilience of buildings to the effects of hygrothermal loads
No full textPeer reviewed: NoNRC publication: Ye
Laser-induced breakdown spectroscopy of molten matte
No full textLaser-induced breakdown spectroscopy (LIBS) is an atomic emission spectroscopy technique suitable for in-situ and in-line measurements during pyrometallurgy. A mobile prototype system was developed to measure elemental compositions of molten metals. An inert gas flows through a tube with one end immersed in molten metal and the gas bubbles out below the melt surface. The LIBS measurement is made through the tube and onto the bubble\u2019s surface. This avoids measuring surface contaminants and slag. This paper presents the simultaneous measurement of Cu, Ni, Fe, Co, and S concentrations in molten matte at 1,125\ub0C.La spectroscopie des plasmas induits par laser (LIBS, de l\u2019anglais Laser-induced breakdown spectroscopy) est une technique de spectrom\ue9trie d\u2019\ue9mission atomique pouvant \ueatre utilis\ue9e pour les mesures in-situ et en ligne durant la pyrom\ue9tallurgie. Un prototype de syst\ue8me mobile a \ue9t\ue9 d\ue9velopp\ue9 pour mesurer les compositions \ue9l\ue9mentaires de m\ue9taux fondus. Un gaz inerte s\u2019\ue9coule le long d\u2019un tube dont l\u2019extr\ue9mit\ue9 est plong\ue9e dans un m\ue9tal en fusion. Le gaz s'\ue9chappe en faisant des bulles sous la surface du m\ue9tal en fusion. Les mesures LIBS sont effectu\ue9es \ue0 travers le tube, sur la surface int\ue9rieure des bulles et sous la surface du m\ue9tal fondu. Ceci permet d\u2019\ue9viter de mesurer la scorie ou les contaminants en surface du bain. Cet article pr\ue9sente les mesures simultan\ue9es des concentrations en Cu, Ni, Fe, Co et S dans la matte en fusion \ue0 1,125\ub0C.Peer reviewed: YesNRC publication: Ye